1.0  DRAKE MODS (09 NOV, 1996)

         This document is considered public domain and you are free to distribute
         this  document in its entirety without alteration. No fees or payment is
         to be granted or collected in the distribution of this  material.  While
         reasonable  effort  has been made to ensure accuracy of data, the author
         assumes no liability or  responsibility  for  the  consequences  of  any
         action on the part of any reader through the use of this information.

         Enclosed  are  a  number  of  mods available for various pieces of Drake
         equipment of the 4 series and later. Some of these changes I  have  per-
         sonally  implemented  and  some are collections from other sources. I've
         stayed on 'the straight and narrow' in  providing  nothing  radical  and
         kept the changes to the refinement level.

         What I've tried to do here is not only list the mods that I know of, but
         to  share  some of my experiences with the equipment. I've included some
         historical information and some thoughts on what the B and C series  are
         about. A large part of the reason for this is that I've had to find this
         out myself - the hard way. A lot of the data is what I would of liked to
         have known before I started to acquire some of this gear. What surprised
         me  most  about  this equipment is that there is almost no data external
         from Drake available. No mods - and I searched every where. No knowledge
         of what makes a particular example a good one. I was on my own, and try-
         ing to not just render my gear serviceable, but restore  it  also.  Just
         what  do  you do with a mechanically unstable PTO? Is it possible to fix
         it? What is the VOX behavior of a properly operating  TR7?  And  so  on.
         With  but one or two minor exceptions, every unit listed I have had some
         experience with, but not all of the mods have been deployed. Mods  obvi-
         ously  have been found. Some of them are from my having bought my latest
         flea market 'works great - just aligned' joy home,  cracked  the  covers
         and  WHOOOOOOA!  Whats  *this*? (ever seen someones attempt at turning a
         Heath HR20 into a base for a radio telescope? don't ask).

         You'll find this document a little different than  most  'mod  strings'.
         The  reason  for  this  is that if you screw up (say) a Kenwood mod, you
         just put the mess in a box, take it to a dealer and throw some money  at
         him.  Well, I'm sure you've noticed that Drake dealers are in short sup-
         ply these days. AND surprise surprise - while a lot of technicians might
         be able to service a multi loop PLL synthesizer, they have never seen  a
         12AX7 or have a clue just how a glassFET works.

         As  a  general  rule,  modifications are to be avoided unless there is a
         specific problem to be addressed or a refinement to be add.  I  strongly
         recommend  that  you do not make any equipment changes unless there is a
         good reason to do so. The only reason to modify a piece  of  well  engi-
         neered  equipment  is  to fix an oversight or add a capability that cur-
         rently does not exist. You should never modify equipment  unless  it  is
         working  as  well  as  it could. Modifying equipment that is not working
         properly will only make it work .... worse.

Drake Mods (09 Nov, 1996) 1

         1.1  GENERAL

         Comments in this section are generally common to all Drake 4 line equip-

         o   Some Notes Regarding V5

             This  listing  seems to be well distributed. Please DO NOT strip the
             TR7 data out of this ZIP file. I've had people call me for this data
             as DRAKEMOD says it is included. The disclaimer  says  "...  in  its
             entirety". The entirety means the ZIP file that contains 3 files.

             I  did  inadvertently  make a Drake enthusiast. This individual went
             out and bought a TR4Cw/RIT just from reading this and  seems  to  be
             thrilled. This is quite a compliment.

             What  I've learned through my use and ownership of this Drake equip-
             ment from R4B/T4X to the TR7 is that it is amazing  how  little  you
             need  to  have  some  fun  and yes, even be competitive. As has been
             proven time and time again in other pursuits, it is not  the  equip-
             ment as much as it is opportunity and user skill. High end equipment
             might  make it easier ... and then again, maybe not. Well engineered
             equipment is eternal. Amateurs have been using CW since day one  and
             SSB  for  40  years. What applied then applies today and largely has
             not been improved upon all that much. Its  gotten  smaller,  lighter
             and  consumes  much  less  power.  However, it is not much more than
             application of modern technology to well established  communications

             My personal experience with other manufacturers Amateur equipment is
             not  bigotry  or  xenophobia. The world has changed - a lot - in the
             last 5 years. Modern consumer electronics has invaded Amateur radio.
             What you can buy today, you'd have sold your soul for 10 years  ago.
             Unfortunately,  its  unserviceable  by  most  and like most products
             these days value evaporates in front of you. Whatever you  buy  new,
             such  as  personal computers and Amateur transceivers, is obsolete 6
             months after purchase. Considering Amateur HF equipment, well  engi-
             neered 'old tech' is applicable 90% of the time for 25% of the cost.
             And  the average mortal can service it with basic test equipment and
             a reasonable application of theory.

             For whatever your reasons for enjoying Drake equipment -  nostalgia,
             preference, curiosity or whatever I hope you find this useful. Worst
             case, then, at least an entertaining read.

             Here's DRAKEMD5. Enjoy.

         o   Swap Nets

             Do  not expect these nets to specialize entirely in Drake equipment.
             Some nets have specific  rules  regarding  acceptable  equipment  to
             advertise.  In  general,  no CB equipment unless modified to Amateur

         Drake Mods (09 Nov, 1996)                                              2

The times mentioned are local Toronto time.

         o   How Drakes Age


             All  kidding  aside, most Drake equipment will not self destruct un-
             less provoked. After all this time, just about any component that is
             going to fail, has. Here is a brief list of what is likely to happen
             with a Drake over time:

             -   Electrolytics dry out

             -   Some ceramic capacitors fry from excessive heat.

             -   Preselector verniers wear

             -   Worn switches - selector tabs

             -   PTO end play needs adjustment

             -   PTO lubricant dried out

             -   Tube failures

             -   User modifications

         Drake Mods (09 Nov, 1996)                                              3
             Not  much,  really. You can use this as a check list of what to look
             for or what to service when you buy your 'new' Drake.  The  first  8
             items or so are operational and not cosmetic.

         o   PTO End Play

             If the tuning knob can be wiggled from side to side, chances are the
             end play needs adjustment.

             End  play  can be adjusted by tightening the ball bearing on the PTO
             tuning worm gear. Some Drake equipment might have an extra  hole  on
             the  PTO cover for this purpose. For those that do not, you must re-
             move the PTO cover. Use a long 3/32" allen (hex) wrench. The adjust-
             ment 'nut' in question is recessed beneath the  coil  form.  Do  not
             overtighten  or you will ruin the dial drive ball bearings and race.
             Do not disturb any placement of components or you  will  affect  the
             PTO dial tracking.

         o   PTO General Notes

             Most  of  the PTO units are much the same throughout the 4 line, but
             the drive mechanisms and indicator plates are not. The worst  things
             you  can do to a Drake PTO is to continue tuning past the STOP indi-
             cation or clean the dial plates with something  that  dissolves  the

         Drake Mods (09 Nov, 1996)                                              4
             plastic. Be very careful with cleaner on those Lexan dial plates! If
             in  doubt,  use  mild soap and warm water. Dial plate replacement is
             impossible (there are no dial plates to be had). Drake will  service
             the PTO for you - they have the gears and other mechanical parts and
             can  reset  the  PTO  for drift and linearity spec. It would be most
             wise, however, to not lunch the PTO gears and dial plate.

         o   PTO Evolution

             The PTO stayed basically the same over the  years.  It  is  a  good,
             solid  design.  Early  model PTO assemblies had a brass pin that was
             driven into a slot in the gear to provide a stop.  As  these  assem-
             blies  wore,  sometimes the pin would not extract itself and the PTO
             drive would end up in a locked state. If this was  forced,  the  pin
             will  snap,  leaving  no dial stop at all and the dial plate will go
             around and around until the slug bottoms.

             Later assemblies used nylon gears and dual dial plates on a  concen-
             tric  shaft. Some of these dial plates are 3 pin and some are 2 pin.
             The number of pins refers to the brass rivets  that  hold  the  dial
             plates  to  the  gear  faces.  There is no stop to speak of in these
             assemblies and turning past the mechanical resistance of  the  drive
             assembly  will  lunch the gears. These PTO drive assemblies may have
             'ears' and there may be 2 ears just behind the gear assemblies.  The
             purpose  of these ears is to allow the dial plates to be rotated for
             proper mechanical orientation with the dial window gradical.

         o   PTO Mechanical Instability

             This is usually caused by either the worm gear  tension  spring  not
             hooked  to  the  aluminium PTO cover or by the end cap on the end of
             the PTO coil form being loose. If the problem  is  not  the  tension
             spring,  remove  the  PTO  cover and look at the end of the PTO coil
             form. You will see a cap on the end of it. It should not  be  loose.
             If  it  is  loose, carefully remove it, apply some glue and stick it
             back on. The coil form is delicate! The end cap just  has  a  square
             hole through which the tuning slug brass rod goes through. For glue,
             I use GOOP.

             See also PTO End Play above.

         o   PTO Warble

             Sometimes the PTO will warble slightly while tuning. This is usually
             caused  by dried out grease on the drive mech ball bearings. This is
             the ground path for the PTO slug drive which has a brass rod inside.
             Fix  the  dried  out  grease  problem  first.  Use  Teflon  lube  or
             Lubriplate.  Run  a flexible ground strap from the PTO drive yoke to
             ground. Do not grease or lube the top guide pin  for  the  PTO  slug

         o   PTO Lockup - B Series

Drake Mods (09 Nov, 1996) 5

             Sometimes  the  brass  pin  will  insert into the gear at the 'STOP'
             area, but it will not extract itself, causing the  PTO  assembly  to
             lock  up.  Wear will cause this, but in a lot of cases its caused by
             the gear timing being off a little bit. What happens is that  you'll
             buy a used 'B' and use it. One day, you'll hit the stop, and the pin
             will lock the PTO. Oh Oh - whats *this*?

             Unlock  the  PTO  first  by pushing the stop pin back and rotate the
             tuning knob. Looking at the front of the radio, you'll notice a  ny-
             lon  gear thats spring loaded. Gently push this gear back and rotate
             the tuning knob ever so slightly (which way? take  your  pick).  Now
             run  the  PTO to the stop again and see if the pin extracts. No? You
             went the wrong way or there are more serious problems.

         o   PTO Lubrication

             Given the age of these unit, the grease is starting to dry out.  Its
             possible  that  it  may  even has run away slightly after seeing God
             knows what use in a car or in a hot tent on  Field  Day  many  years
             ago.  Most  important  is  to lubricate that worm gear. I use Teflon
             spray lube. Just use the slightest bit. Too much is much worse  than
             too little. The dial mech should offer only slight resistance to the
             tuning  knob.  You  should  be  able to fast spin the tuning knob by
             placing your index finger on the outside of the  knob  and  rotating
             your hand. If you cannot do this, then you have some kind of a prob-
             lem in the PTO dial mech.

         o   PTO Backlash

             Inspect the brass rod that extends from the rear of the PTO cover as
             the  unit  is tuned. It may be discolored, but it should not be cov-
             ered in grease and guck. This rod and the end of the PTO tuning coil
             comprise the end bearing. Clean with  alcohol  and  a  paper  towel.
             Sometimes  'junk'  will  accumulate  in this area and actually cause
             some binding in the tuning slug. You'll tune the PTO and in about  5
             minutes, it will 'jump' frequency up to a few hundred cycles.

         o   PTO Drift

             All  Drakes  drift. Once warmed up and settled down, they are satis-
             factory for all modes but RTTY. For all practical purposes, the  PTO
             from  the B series to the TR7 (excluding the TR5) are identical with
             the exception of the dial plates and the markings on  the  aluminium
             cover box.

             In  very  general  terms,  the PTO should settle down within about 5
             minutes after turn on and be usable. It will still shuffle around  a
             bit after that, but you should not be chasing it continuously.

             There  are  no  PTO  adjustments  available to compensate for drift;
             components were 'selected in production'. In extreme cases, you will
             either replace the PTO from a junker or send the unit to Drake for a
             rebuild. Expect to pay for 4 quarter hours labor minimum.

         Drake Mods (09 Nov, 1996)                                              6
             Inability  to  have  the  C line dial plates to indicate exactly the
             same frequency after moving away 100 kHz or so and returning to  the
             same  frequency  is usually caused by the rubber collar under tuning
             knob and dish. After all these years, the rubber has hardened or has
             worn. Replace the PTO rubber. The C clip should not be tight against
             the aluminum washer and the washer should be installed such that the
             groove around the perimeter is on the outside.

             While you've got the knob and dish off, inspect the shaft for burrs.

             Sometimes when you push a new rubber collar on you'll  displace  one
             of the gear sets. This is easy to fix, but you'll have to remove the
             top  cover, push the left hand ear to the right while gently rocking
             the tuning shaft and pulling out. Then align the dial plates  again.
             A new collar should last for years.

         o   4 Line Dial Plate Dish, Knobs etc.

             Personally,  I  don't like the plain dial skirt on the C line. I re-
             place them with TR4  dial  dishes.  This  does  nothing  except  for
             appearance and is a matter of personal taste.

             The TR7 dial dish is different than the 4 dial dish.

             Some  dial knobs are thicker than others depending on the PTO assem-
             bly. Most  knobs  are  available  for  replacement  except  for  TR7
             bandswitch knobs. Unobtainium.

         o   Mixing Scheme

             First  mixer injection on all T4/R4 is premixed from the PTO and the
             band crystal. The crystal is always 11.1 MHz higher than the low end
             of the band edge in question. For example, the 80  meter  band  will
             have  3.5  + 11.1 = 14.6 MHz crystal. The PTO is mixed with the band
             crystal and the difference is  used  and  injected  into  the  first
             mixer.  A  lower  PTO frequency correlates to a higher received fre-
             quency in the band range.

             Using 160 meters with a 12.6 MHz band crystal  for  example,  the  0
             scale  band  edge is 1.5 MHz. The first mixer injection frequency is
             Fin + Fif = 1.5 + 5.645 = 7.145. This is made from the difference of
             the PTO = Fxtal - Finj = 12.6 - 7.145 = 5.455 MHz. If you apply  the
             above  scenario  to  a 2.0 MHz incoming signal you will see that the
             PTO oscillator frequency tuning is inverted.

             Both the R4any and SPR-4 are remarkably low in spurs and mixing pro-
             ducts once aligned properly. On all of these receivers, I've  always
             noticed a quickly tuning spur at 3.897 MHz. This tunes very fast, so
             a VFO harmonic is involved.

             Because of the PTO frequencies and mixing scheme there are some for-
             bidden  zones  of  operation on some band segments that will produce

         Drake Mods (09 Nov, 1996)                                              7
             very foul mixing products. Obviously the band range covered  by  the
             PTO  is  a no-no. 10 MHz operation is possible, but pay attention to
             the transmitter manual, for the PTO second harmonic is an  important
             consideration  when  the  twins are set up for transceive operation.
             None of these zones fall into current amateur band assignments.

             This also explains why strange settings of the  preselector  control
             produce receive peaking - you are likely finding a mixer output that
             could  be  PTO,  crystal  or the sum of the PTO/crystal product that
             coincides with the rack slugs for the front end tuning.

         o   R4any and T4any Transceive Operation

             Transceive selection and muting  is  accomplished  through  the  INJ
             line.  This  is done by supplying a high negative voltage along this
             line from the unit with the active PTO. This line is routed  to  the
             link  on  the preselector and to the control grid of the PTO/xtal LO
             premixer. There is also a diode on the  preselector  mixer  more  or
             less  from  screen grid to plate. This forms an electronic switch to
             kill the premix on the unit that is having the external  PTO  premix

             On the R4C/T4C there is also a separate BFO line. The oscillators on
             both  units  will fall into sync with each other naturally just from
             being linked together, providing they were pretty close together  to
             begin  with.  If the BFOs won't sync, make sure you are using RG/62U
             cable and that the oscillators individually are pretty close.

         o   Mixing Scheme - TR4any

             The TR4 uses the same PTO as the rest of the 4 line, but it has a  9
             MHz  IF. It covers 80 to 10 meters. Hetrodyne mixer crystals are not
             used on 80 or 20 meters. For these two bands, either the sum of  the
             IF  and PTO is used (20 meters) or the difference (80 meters). Thats
             why 20 meters has its unique dial markings that are backwards to the
             rest of the bands. All other bands have premix crystals  and  follow
             the  formula  of  Fxtal  = F + 9 + 5.0. The injection into the first
             mixer is 9 MHz ABOVE the the lower band edge and is made up from the
             band crystal frequency MINUS 5. All crystals are HC/6U 3rd overtone.
             This is accurate for all bands but 80/20. In this case no crystal is
             used and the 5-ish MHz PTO is used directly.  The  6EA8  PTO  premix
             circuitry  is diabolicly ingenious in how it uses and does without a
             crystal oscillator depending upon the band switch.

             Having a TR4 operate on different bands is more of an operation than
             simply changing crystals. The front  end  is  tuned  by  a  variable
             capacitor, not by slug racks as in the case of the R4any.

             Moving a TR4 to the WARC bands, say 18 MHz in exchange for 20 cannot
             be  done  (no  crystal,  remember?). Generally, what you see is what
             you're going to have and depending upon what you do and how  you  do
             it,  be  prepared  to kiss 15 meters goodbye. That band 'falls' into
             alignment by default from the alignment of  the  other  bands  being

         Drake Mods (09 Nov, 1996)                                              8
             These  are not available from Drake any more. Use cleaning materials
             with extreme caution.

             Most minor scratching of clear plastics can  be  polished  out  with
             toothpaste, a touch of water and a paper towel. This works amazingly
             well.  If  you  use this trick on the dial plates, be careful you do
             not rub the lettering off. Gel does  not  work  nearly  as  well  as

         o   C Line Dial Alignment

             The  C line allowed for dial indication alignment through the use of
             idler gears in the dial drive mech. Just to the left  and  right  of
             the  drive  transmission  you  will  find one or two 'ears'. Pushing
             these ears towards the PTO shaft will allow the indicator plates  to
             be  rotated  such  that the plates align to display the correct fre-
             quency. Depending upon the age of the C line unit in question, there
             may only be one ear. In order to reseat the idler gear, push the le-
             ver over and let go such that it snaps into place. If you do not  do
             this,  it will take some rotation of the tuning knob until the idler
             seats and your alignement will be off (again!).

             On the B, you can rotate the Lexan dial plate a little with a  touch
             of  brute  force.  Place a small screwdriver on the edge of the dial
             plate and flick it the few necessary degrees. Do not  to  this  with
             the C line (see above).

         o   Dial Plate Scraping

             The  dial  plates  are  fairly  large diameter Lexan disks. On the C
             line, there are 2 of them. One knob turn tunes the receiver 25  kHz.
             Sometimes  the  dial  plates will scrape as they are rotated usually
             somewhere around the front panel. Over the years, some heat  warping
             should  be  expected.  Quite  often though the scraping is caused by
             poor assembly after removing the front panel for  cleaning.  If  the
             whole PTO had been removed, there is a little positioning adjustment
             available if the 3 PTO nuts are loosened.

             Ensure  the dial gradical plastic is on the outside of the sub chas-
             sis with the red line on the inside of the window (C line).

             On all radios, the blue filter mounts on the back of the white plas-
             tic dial backing. Make sure the dial light wires are positioned away
             from the dial plates.

         o   R4any and T4any Tuning Rack

             Leave the slugs alone! There should never be a valid reason to  pull
             a  tuning rack apart except under the most unusual of circumstances.
             These slugs are color coded for permeability - mix  them  up  during
             reassembly  and you'll have a fun time getting the receiver to track

         Drake Mods (09 Nov, 1996)                                              9
             Sometimes  you  may  encounter either a dead radio or an intermitent
             one and just can't find the sore spot. Check the rotary switches for
             a sawed off selector tab. Sometimes just enough of a stub is left to
             select some positions - just barely. This is just wear and tear  and
             is simply the rubbing action of the selector tab going past the fin-

         o   T4any Microphone Connector

             The  microphone connector plug is a Switchcraft S230 and has a diam-
             eter of .210". This was used so you  couldn't  plug  the  microphone
             into  the  earphone  connector  and have the output fry the element.
             These plugs are a little rare. The reason why the PTT  line  is  the
             tip  and  not  the  ring is simple. If it were the other way around,
             you'd put the keyed line across the mic element as  you  pushed  the
             connector  in.  In  desperation,  I've  seen  a standard 1/4" stereo
             socket used and it could  be  an  expensive  expedient.  Microphones
             don't make good speakers or speakers for very long.

             These   connector   assemblies   are   no   longer  manufactured  by
             Switchcraft, although there is possibility of a  limited  production
             run. Check with Mouser Electronics regarding status (Oct, 1996).

         o   T4 and TR4 Relay Cycling

             With  the  age of these units some of the electrolytics are starting
             to dry out. Sometimes they'll go leaky from cell to  cell  if  there
             are  multiples  in  the can. If you have problems with the T/R relay
             chattering or cycling, quite likely it could be one of these  filter
             cans. The only way to roughly suspect an element has gone is to clip
             in  a  100  Uf  300 volts across an element. If the cycling stops or
             slows down this is the likely problem. Beware of some funny problems
             you may get with cell to cell leakage, however. These can be  tricky
             to nail.

             These  canned  capacitors  are  dated and largely unavailable as re-
             placements. Due to their age, even if replacements  were  available,
             you  wouldn't want them. Whether in use or not, they've been sitting
             on the shelves for too long. Modern capacitors are much  better.  My
             recommendation   is   to   replace   the  whole  can  with  discrete
             electrolytics. You can either leave the old cap in there for appear-
             ances or pull it and put in a hole plug.

             In the receivers, weak power supply electolytics  are  characterized
             by  hum,  low B+ and 'funny' audio on SSB. The funny audio is caused
             by harmonic mixing of the 60/120 cycle hum and the  detected  audio.
             In  this  case, sometimes there is not enough hum out the speaker to
             be too objectionable, but the speaker audio sounds 'funny' for  some
             reason  or  another. You can verify this with the calibrator on SSB.

         Drake Mods (09 Nov, 1996)                                             10
             As you sweep across the calibrator slowly, you'll  hear  some  spots
             where  the  audio goes muddy. Once you detect it, and have your ears
             trained, its very obvious.

         o   Schematic Date Codes

             On  the  4 line B series and above you'll notice a series of numbers
             in small print on the schematic. I have an T4C  schematic  with  the
             numbers  10077626470.  This  is in mmddyy/serial no format. It means
             that this schematic was revised on October 7, 1976  and  applies  to
             serial  numbers  above  26470.  I do not see this notation after the

         o   Drake Equipment Wiring

             Drake did not color code their wiring to any appreciable degree.  In
             most  cases, their hook up wiring seems to be white colored and some
             wires may have a color trace. More than one wire may have  the  same
             color  trace, so be careful and verify with an ohm meter from end to

             Additional care should be used when soldering to Drake hook up wire.
             The insulation melts very, very easily and will crawl  up  the  wire
             and  peel off while doing so. When replacing items like those canned
             filter caps, sometimes it causes less damage and is  more  expedient
             to  simply  cut  the wires. One can easily and quickly loose 3/4" of
             insulation just in desoldering.

         o   Line Cords

             Some line cords will be 2 wire - no ground pin. This may  appear  on
             the  receivers  or  on  the  AC4 transmitter power supply. Users are
             urged to change the line cord to  a  3  wire  configuration  with  a
             grounded  centre  pin.  Without this centre pin, the chassis leakage
             will float to about 50  volts  AC.  In  the  event  of  the  primary
             windings shorting to the chassis, this can prove to be lethal.

             Don't put this off! Replace that line cord.

         o   Loose Knobs

             On  some controls it may be difficult to keep the knobs tight to the
             shaft. Overtightening will split the knob. Quite often  the  problem
             is  simply  caused by the knob not being exactly square to the shaft
             flat when the set screw is being tightened. Rock the  knob  slightly
             while  tightening  the setscrew. The knob setscrews are not all that
             easy to deal with in the long term. A better setscrew  is  an  Allen
             (hex)  head  screw. This type of setscrew will provide better torque

         o   Sensitivity Check - all Drake 4 line

             All Drake receivers and transceiver should provide a noise  peak  as
             the  preselector  is  passed across the tuning range, even on 10 me-

         Drake Mods (09 Nov, 1996)                                             11
             ters. If your equipment does this with  no  antenna  connected,  you
             have all the sensitivity you can use. If it fails to provide a peak,
             alignment  is  immediately suspect. Generally, the calibrator should
             provide  an  S9 meter reading on 10 meters, progressively increasing
             as the band switch is rotated to 80 meters.

         o   Front Panel

             The 4 line has spacers in the 4 corners of the front panel. Be care-
             ful when you remove the front panel. The thickness  of  the  spacers
             seems  to be 1/16" or so and they are, of course, black. They disap-
             pear as soon as they hit the ground.

         o   Screws and fittings

             There are no metric fittings that I know of.  Most  of  the  machine
             screws  are  4/40,  the  case  cover screws are 6/32 and the chassis
             sheet metal screws are usually #4.

         o   Speakers

             All  Drake  equipment  is  standardized  to  4  ohm  speakers.  This
             impedance  is  important. Use of 8 ohm speakers will produce consid-
             erably less audio output and is not recommended.

             On all the Drake C line and before, as in  all  audio  power  stages
             that have an output transformer, never crank up the audio gain with-
             out  a  speaker  attached. Never connect an A/C voltmeter across the
             primary. Transients generated in the output transformer,  especially
             without  a  load,  will  create very high voltage spikes through the
             collapsing magnetic field. This is  how  output  tubes  arc,  output
             transformers short and voltmeter rectifiers get punctured.

         o   Power Supplies

             The  Drake  vaccuum  tube transmitters and transceivers use the same
             AC/3 or AC/4 supply. When using alternate supplies such as the Heath
             HP-20 or HP-23 ensure that the low voltage 250 volt supply is indeed
             this level. Do not provide more than 265 on this power line.

         o   Transmitter Meter PA Current Resistor

             When you buy your 'new' Drake, check the  value  of  this  resistor.
             I've seen a number of these cooked. Usually they go higher in value,
             causing a number of problems. With the resistor higher in value, the
             meter  will  read  higher.  You'll  end up setting the bias too low,
             causing poor transmitted audio.

             It would be wise to verify the meter calibration against the  idling
             current. Using the T4C for example, it has its PA bias set for 70 ma
             and has a meter resistor of 3.3 ohms. Set to 70 ma, you should meas-
             ure  E=I*R,  or  .07*3.3 or .231 volts across this resistor. Measure
             across the resistor and NOT at the meter terminals.

         Drake Mods (09 Nov, 1996)                                             12
             Similar problems with setting the proper idling current will be  ob-
             served if the PA current meter needle is not resting at zero.

         o   Intermitents

             Some  intermitents may be difficult to find and somewhat hard to ex-
             plain. Inspect the bottom of the chassis carefully and you will  ob-
             serve  screws  holding  down terminal strips and circuit boards. All
             the screws that you can easily access should be backed off 1/2  turn
             and retightened.

             A  TR3  suffered  the  above problems and was cured by the above ap-
             proach. Most of this equipment is 20 years old or older. In the case
             of the TR3, it was 33 years. The obvious suspect is corrosion.

         o   Drake Tube Transmitters - ALC

             On all Drake Tany and TRany radios,  the  transmitter  ALC  is  very
             aggressive. In use, you won't see the output meter kick up that much
             or  the  PA current on the meter of the transceivers move as much as
             you think it should. Usually an output meter  will  'only'  indicate
             about 50 watts or so. This is 'OK' and is *not* an indication of low
             sideband  output.  Actually,  this  is  normal  behavior and if your
             transmitters do not behave this way, expect some ALC problems.

             For a typical Sure 444 or Heath HDP-21 microphone, the transmit  au-
             dio  gain/drive control should be set around the 11 o'clock position
             and the PA current meter should kick up to about  50%  full  current
             (150 ma, T4; 220 ma, TR4).

         o   Transmitter switching

             For all receivers and transmitters in the 4 series the keyed voltage
             level is negative. The TR7 has a positive switch line.

         o   Transmitter Driver Alignment

             Drake  goes  into considerable detail on use of a loading network to
             align the 4 series transmitters. Don't bother. Just align  carefully
             for maximum transmitter output at a low drive level.

             The  reason  for  this  network  is to simulate the loading when the
             units are used in transceive. The better  method  is  to  slave  the
             units  with  the  covers  off  both the receiver and transmitter and
             align. This is much faster and much  safer  than  playing  with  the
             loading  network  method. There is some serious voltage inside these
             units. Align each individual unit and then align in transceive  both
             ways  -  active  PTO  in  the  receiver for the transmitter and con-
             versely. When setting up in transceive,  you  really  only  need  to
             touch  up  the  most rear trimmer bank in the receiver and the front
             bank in the transmitter. It is not as much a pain as you would think
             and once set, you're done almost for life.

             The loading network method is a waste of time.

         Drake Mods (09 Nov, 1996)                                             13
             Proper  set up of the neutralization is important for a stable, easy
             to tune, low spur transmitter. I've seen numerous methods  over  the
             years, but this works best for me.

             What  you  want  to do is set the neutralization capacitor such that
             the plate current dip and output occur at  the  same  point  in  the
             final tuning controls. You need a decent dummy load.

             Start  on  20  meters and feed enough drive in the tune position for
             about 200 ma of current. With the LOAD capacitor at maximum (lightly
             loaded), tune for maximum output on the  wattmeter.  Now  watch  the
             plate  current  meter  as  you  rotate it off resonance. Does it dip
             lower? Take the transmitter (transceiver) out of 'tune'  and  adjust
             the  neutralization  trimmer  about 10 degrees. Repeat until dip and
             maximum output occur at the same time. Once you have it  set  up  on
             20, then move to 10 (or 15).

             The  reason  for  starting  on  20  meters  is  for  safety.  If the
             neutralization is far out to begin with, the PA  stage  will  oscil-
             late. It is also easier to adjust initially on a lower frequency.

             WARNING:  The  neutralization trimmer has a lethal voltage on it! DO
             NOT adjust with the transmitter operation, DO NOT touch the blade of
             the screwdriver while adjusting.

             Or go ahead. Ignore these warnings. I'll have less  QRM  to  contend

         o   Transmitter Tuning

             The best final tubes to use are Sylvania. The 'generic' 6JB6 are OK,
             but they can present alignment problems.

             The  6JB6 tubes will draw considerable current. On the TR4, they can
             draw upwards to 450 ma. The T4 will draw 325 or so. When tuning  up,
             keep  the  drive level on either unit to 150 ma or less until you're
             close to the final settings.

             Low PA tube life is usually caused by bias setting,  operator,  SWR,
             heat  or  PA  neutralization. The 6JB6 tubes are being pushed a bit,
             but they should offer a good service life if properly set up,  oper-
             ated  and  kept  reasonably  cool.  I've heard that tubes don't need
             cooling since its the glass that's getting hot, but the real heat is
             on the plate, insulated by a vaccuum. Nice theory, but my experience
             indicates otherwise. Besides, if for no other reason, all that  heat
             cannot be good for component life.

         o   Transceive Operating

             Any  of  the 4 line separates will transceive amongst themselves but
             only within the same band and only within about 50 kHz, depending on
             the band. When there is a difference in the series set to transceive

         Drake Mods (09 Nov, 1996)                                             14
             some minor inconveniences will be suffered such as  loss  of  active
             PTO  indication  and  the  requirement of BFO netting prior to oper-

             But it will work.

         o   T4B/R4B Transceive Set Up

             Since  this  equipment  does not have a separate BFO injection line,
             you must net them manually in order for them to transceive properly.
             The C line provided a separate line. There is more to this, however.

             Before netting the two together, you should verify the BFO frequency
             of the T4any is on frequency. It is shifted for CW operation. If  it
             is off frequency, then netting the two together may cause the offset
             to be quite wrong on CW.

             Proper  netting  on the T4any is best done with a receiver that does
             not shift frequency  between  upper  and  lower  sidebands  (like  a
             Drake).  Talk into the TX on a dummy load while tuning a known prop-
             erly set up  receiver  using  headphones.  Switch  to  the  opposite
             sideband  and  adjust  the BFO trimmer on the transmitter to exactly
             the same pitch/frequency. You may have to do this a few times.

         o   C Line Meter Switching

             The C line used an articulated LOAD control shaft that, when  pushed
             in,  would switch the meter from PA cathode current to relative out-
             put. The push required is considerable and is a result of the spring
             strip tension and the spring in the return switch. Never try to  ad-
             just the tension of the shaft spring strip by squeezing it. The bend
             in  the metal strip is a stress point and the strip will fracture at
             the bend. There are no replacement shafts to be had. If the  tension
             is  abnormally high, ensure that the shaft coupler and the shaft it-
             self are completely seated to the LOAD variable capacitor.

         o   Noise Blanker Set Up

             Both the R4C and TR4 noise blankers are very effective.  The  align-
             ment  of either is not difficult except in the case of the TR4 where
             access to some tuning adjustments can be a challenge.

             You'll need a 'scope to completely set one up and/or an analogue me-
             ter. Digital meters are OK, but they don't  show  relative  measure-
             ments very well.

             The components in parenthesis are TR4 part tags for the 34PNB.

             Turn  equipment  on  (what else?), turn noise blanker and calibrator
             on. Tune calibrator in on 10 meters and  misadjust  preselector  for
             about  an  S3  reading. Adjust C3 and C6 (C10 and C19) for maximum S
             meter reading. Place a 'scope probe to the base of Q12  (Q12)  or  a
             voltmeter  to the emitter of Q14 (Q14). Peak preselector. Adjust C19
             and C25 (C8 and C21) for  maximum.  Turn  off  calibrator.  Set  the

         Drake Mods (09 Nov, 1996)                                             15
             'scope  probe  for 1/10 (low capacity probe). All tuning adjustments
             are finished. No more  trimmer  twiddling  from  this  point!  Place
             'scope  probe  to drains of Q7 and Q8 (Q6 and Q7) and adjust R28 for
             minimum. Finally, on the R4C only, adjust the gain balance for simi-
             lar  S  meter  reading  on the calibrator with and without the noise
             blanker and the jumper plug.

             If you do not have a 'scope to adjust R28, leave it alone or more or
             less centre the control.

         o   Transmitter filament Fuse

             Most Drake transmitters and transceivers have a fuse in the filament
             power. This fuse may be a strand of copper wire or a pig tail  fuse.
             It is a wise safety feature and prevents the wiring harness from go-
             ing  up  in  smoke  should a tube filament short. Pig tail fuses are
             hard to find and single strands are cheap, but  a  pain  to  create.
             Should your fuse open, install a fuse block for a 3AG fuse holder by
             bolting  through  one  of the chassis perf holes. This is a no holes
             mod and worth while. Don't forget to find out why the fuse opened in
             the first place. Sometimes, they DO just 'go'.

         o   Carrier Balance (all transmitters and transceivers)

             The procedure in the manual is to use the relative output meter  for
             carrier balance adjustment. The output meter is not sensitive enough
             to  do  this  adjustment properly. Use an external receiver and make
             sure the mic gain is fully CCW. You should be able  to  almost  null
             the carrier out completely.

         o   Crystal Filters - Hope

             Rumor has started that the original manufacturer of Drake filters is
             about  to  begin production as of mid October, 1996. This has yet to
             be confirmed, but if it is true, filters should be available by  the
             end of the year.

             If they do not appear by then, all bets are off.

         o   R L Drake Inc

             Drake  has  in  stock replacement parts for most of their equipment.
             For items that are in excess of 15 years old, this is very good.  In
             most  cases  their  prices are good. One can obtain coils, crystals,
             tubes, meters and relays. Final variable capacitors  are  available,
             but expensive. Most front panels are available for around $15.00 but
             Drake  won't  sell you a new one unless you return the old one. I do
             not know why, but Drake is adament on  this  policy.  If  you  write
             Drake  a  letter  they  will  ship off a computer listing of current
             parts stock for a particular  radio.  As  of  the  Summer  of  1995,
             considerable  parts  were  available for the 4 line et al. Parts for
             the TR7 were few except for ICs and transistors.

Drake Mods (09 Nov, 1996) 16

             There are no accessories available of any consequence. You will  not
             be  able  to  buy noise blankers or crystal filters for any of the C
             Line. If you want crystal filters, there is only one known source  -
             International  in  Florida.  Their filters are much better than what
             Drake  supplied  and  expensive. Well, maybe not that expensive con-
             sidering current KenYaeCom prices. And even their filters are  infe-
             rior to Internationals.

             Essential  parts  are  still  available (until the stock is gone) at
             reasonable prices. If you need accessories for your R4C or TR7, best
             to get them with the radio.

             Drake still services all of their amateur equipment, but they do not
             stock the PA tubes. They charge by the 1/4 hr. The current  rate  is
             about  $17  US. I have heard some 'mutterings' about the labor cost,
             but have yet to hear ANY complaint about the  quality  of  the  work
             done. Consider Drake your only commercial repair service area, espe-
             cially in the case of the TR7. The TR7 (and possibly other equipment
             in the '7' series) requires a fairly high skill set to service prop-
             erly.  Most,  if not all 'dealers' of the, uh, other equipment won't
             touch it. Use this as a warning also for some Drake equipment on the
             dealer shelves, again, especially  the  TR7.  Most  are  consignment
             sales. Consider its status as 'indeterminate'.

         The  differences between the B and C line receivers will be discussed in
         separate detail. Even the C line receivers were different as  the  years
         progressed.  There  is an overall difference between the C line and much
         of went before, however.

         The B line employed copper plated chassis. In the C, this was done  away
         with. The C series also employed dual concentric dial plates where the B
         series  and even the T4X used a single dial plate. The knob skirt on the
         C line was plain; on the B it was calibrated in kHz and on the TR4  this
         dial skirt just had radial markings with no numbers.

         Generally,  in  the  receivers, Drake made optional on the C a number of
         things that were standard on the B. The B was a complete receiver out of
         the box; the C was not. The B automatically  switched  the  AGC  as  the
         modes  were changed; the C receiver had a 3 position AGC decay time con-
         stant setting that was independant of mode. Additionally, the C receiver
         allowed for more optional band select crystals. The primary  reason  for
         the triple conversion on the C was to allow for crystal filter selection
         and  a  notch  filter.  Pundits  could  argue the necessity of this, but
         regardless, thats what Drake did.

         In the transmitters, Drake switched from a 6HS6 LO premixer to a 6EH7 on
         the C line. This is a higher gain tube, but still, the B series did  not
         suffer  from  a  lack  of  drive.  The  12BY7  was used as a driver tube
         throughout the 4 line. Drake used 6JB6 tubes for the final PA in all  of

         Drake Mods (09 Nov, 1996)                                             17
         their  C  and  B line transmitters. In the transceivers 3 of these tubes
         were used to produce 200 watts output. On the separate  transmitters,  2
         of these tubes were used to produce about 150 watts on 80.

         Most  of the changes in the C transmitter were for operator convenience.
         The C series most notably moved the switch for PA current from  a  sepa-
         rate control on the B to a switch that was activated by pushing the load
         control in.

         The  C  line also improved upon transceive operation of the separates by
         providing a separate line for the BFO. This alleviated  the  requirement
         to  set  the  receiver  and transmitter oscillators exact by the 'canary
         chirp' method. Additional switch lines were also provided  to  the  dial
         lamps to indicate the active VFO when slaved together in the C line.

         Despite  these  changes,  the  B  and C series could be slaved together.
         While the TR7 and TR4 were not transceive compatible with  the  separate
         receivers,  they  still  provided for external receive antenna switching
         and external RX mute. Drake took measures to provide for an intermix  of
         their  equipment  despite  improvements  to  the gear as the years prog-
         1.3  R4B AND R4C

         You could liken the Drake twins operationally to  the  Heath  SB301  and
         SB401  from  the fact that they would transceive. Stand alone SSB trans-
         mitters are all pretty much the same. The T4C is a  bit  like  an  SB401
         functionally.  In regards to the SB301, the Drake 4 line receiver, espe-
         cially the R4C, is in a completely different league.

         All Drake receivers in this series are sensitive and selective.  On  ei-
         ther  series,  a  healthy  receiver  should exhibit noise peaking on all
         bands as the preselector is adjusted with no antenna connected. It  will
         not  be  an extreme increase in noise level, but it should definitely be
         there on all bands.

         Drake enthusiasts generally prefer the B series receiver. The  B  series
         has  built  in a number of items that were options on the R4C. There are
         few mods for the R4B. When you buy an R4B, there is not much else to get
         - EVERYTHING is there that you need - noise blanker,  calibrator  and  4
         selectivity  settings.  The B series was dual conversion, the last IF at
         50 kHz determined the selectivity and provided notch  filtering.  The  B
         receiver  is  noted  for its clean recovered audio, good signal handling
         and solid engineering. Because the selectivity is determined by LC  fil-
         ters,  the  skirt  selectivity is not on par with crystal filter radios.
         Since the B receiver was dual conversion and the C receiver  is  triple,
         it  is generally assumed that the B receiver is 'quieter'. This will ap-
         pear from time to time throughout this treatis and I'm skeptical whether
         this is in fact true or yet another example of theory not  born  out  in

         Drake Mods (09 Nov, 1996)                                             18
         The noise blanker in the B receiver works quite well, but not as good as
         the  R4C or TR4 blanker. The B blanker is more sensitive to noise 'qual-
         ity' - duration, period and rise time. Some noise will be nearly  elimi-
         nated  and  yet  other noise which sounds the same won't be touched. The
         R4C  and  TR4  blankers  are more effective across broader noise charac-
         teristics. The R4B blanker is a 'Lamb IF Noise Silencer'. Detail on  its
         workings  can  be  found  in  most Handbooks dated around 1972. Intermod
         characteristics are not degraded  in  either  receiver  with  the  noise
         blanker turned on.

         The R4C is in fairly high demand. It is a triple conversion receiver and
         completely  different  from an R4B. While the R4B does contain some semi
         conductors, the R4C is more of a hybrid design. There were  at  least  3
         different  types  of R4C receivers. Generally an early R4C has a 4 posi-
         tion crystal filter switch and a later model has a 5 position switch. In
         the later model, the AM filter location was moved inside the chassis and
         mounted on an extra bracket.

         There is no discernible performance difference amongst ANY of the  Drake
         R4C  series receivers. Collectors want the later model; practical owners
         shouldn't care.

         The R4C - in all models - came with an 'OK' sideband  filter.  You  will
         need to upgrade the filters and add some filters if you want to get this
         receiver to perform. There is only one source of filters for the R4C and
         that  is  International  Radio  in  Florida. These filters are expensive
         (about $110 ea. US) and excellent. The most important filter  is  the  8
         kHz  first  IF filter known as a GUF-1. Replacing the stock Drake filter
         with the GUF-1 transforms the receiver. If you have the 6 kHz GUF-1  in-
         stalled, noise blanker performance is compromised. The GUF series filter
         is  difficult  to obtain and they are not drop in replacements. You will
         be required to drill holes in the chassis or build an adaptor board from
         double sided G10 and mount the  assembly  underneath  using  some  stand
         offs. The results are worth it, however.

         A stock R4C is a bit of a waste. Under those covers is goodness just dy-
         ing  to get out. When the R4C came out, there were some compromises that
         had to be made to keep the price point. The trade offs  were  mostly  in
         the  area of filters and no noise blanker. The first IF amp crystal fil-
         ter is a pretty sad excuse and unfortunately sets the character  of  the
         receiver. What you have to do to make it what it could of been is to ba-
         sically  un-castrate  it. With decent filtering and maybe some mods, the
         receiver is as good as and maybe better than just about anything  avail-
         able  to  date. Some aspects of the R4C design cause one to question the
         engineers at Drake. The audio amp in the R4C is frankly terrible. The 12
         volt regulated power supply is an incredibly BAD design. Drake had  this
         'thing'  about  running  transistors from the plate B+ supply using huge
         dropping resistors and zener diodes.  The  above  causes  an  inordinate
         amount  of  heat  to  be  generated.  Regarding the R4C audio amp, it is
         reminiscent of a 60's car radio what with its class A output stage.  Ex-
         cept  for  some  cost savings it was an unnecessary design and using the
         SPR-4 as an example, Drake knew better.

Drake Mods (09 Nov, 1996) 19

         Given all these things to be said about an R4C, why  would  anyone  want
         one?  It  depends if the C in question is loaded or not. The stock audio
         and power supply is offensive from a design aspect, but  it  does  work.
         The  transformation of the receiver with decent filtering is phenomenal.
         What  really  happened  to  the  C  is that Drake cut costs and left the
         underlying receiver alone. That receiver base is  extremely  strong  but
         the strengths are buried by the cost cutting.

         Aside  from  nostalgia  what  makes this equipment attractive is that it
         works, works well, is reliable and of high quality. The AGC on  most  of
         the  receivers  is  superior  to  most  foreign  equipment. Considerable
         thought went into its design. It is overbuilt - you  cannot  break  this
         equipment  through age or use. While it may not have been built with the
         intent for it to still be working 20 years later,  most  of  the  Drakes
         I've seen have had a minimum of repair. All 'old' equipment suffers some
         abuse  as it trades from hand to hand. Surprisingly, the Drake equipment
         seems to survive at the same level as Collins. Rarely  is  it  butchered
         and  then  usually  this happens from an inexperienced person attempting

         Amongst Drake receivers a stock B is vastly superior to a stock C.  Some
         folks  insist  on  having  a late model C - "high serial number" without
         perhaps knowing what they're asking for and willing  to  pay  a  premium
         for.  Fine, if you're a collector. They don't even care what options its
         got, yet if you were to filter up a C and find a noise blanker, it  will
         cost  more  than the radio. The strange thing is all that stock C's have
         is not much more than 'potential'. All work pretty well the same. The  B
         requires  no  work at all and can be had for a song, but don't expect to
         wade through a pile up on 20 SSB with a B - it can't do it, at least not
         very well. The B represents  balance.  It  comes  from  a  period  where
         commercially  available,  cost effective crystal filters where yet to be
         widely available. If you're inclined to have a B after reading this, I'm
         flattered - its an excellent receiver, but it is not  Excalibur.  The  C
         receiver  is  an  incredibly  good receiver, but ONLY if it is loaded up
         with filters. The International filters are better than the filters that
         Drake supplied. The recovered audio on a stock R4C receiver is quite bad
         without some change. Just changing the value  of  1  capacitor  makes  a
         considerable  improvement.  Once  loaded  up,  the R4C becomes a real DX
         receiver and can 'slice and dice' with the best. The only way  to  over-
         load  a  properly set up R4C is to connect the antenna terminal directly
         to the transmitter, its that good. In stock form,  you'd  have  no  idea
         what is there.
         1.3.1  R4C Evolution

         The  information  contained  here is accurate but not necessarily a com-
         plete dossier on the R4C as it changed over the years. Updates  will  be
         made to this section as additional information is acquired.

         o   R4C ser no above 16121

         Drake Mods (09 Nov, 1996)                                             20

Revision date - Feb 1973

             All  mixer tubes 6HS6. First and 3rd mixers cathode injected. Second
             mixer is a dual gate MOSFET. The IF chain following the first  crys-
             tal filter is 6BA6 1st IF, Noise blanker and then 2nd mixer. 4 posi-
             tion filter select.

         o   R4C ser no above 18726

             Revision date - March 1974

             All  mixer tubes 6HS6. First and 3rd mixers cathode injected. Second
             mixer is a 6BE6 with an JFET (2N5459)  buffer.  5  position  crystal
             filter  selection. 3 diodes in series across the S Meter to compress
             the meter range. 2 S Meter zero pots were employed  -  one  internal
             and one external.

         o   R4C ser no above 21000

             Revision date - Nov 1974

             All  mixer  tubes  6EH7.  First and 3rd mixers grid injected. Second
             mixer is a 6BE6 with an JFET (2N5459)  buffer.  5  position  crystal
             filter selection. Some intermediate models in this transition period
             may not have installed the new tapped IF transformer, T7C.

         Amongst the 3 series known, Drake spent considerable effort changing the
         mixers  with particular interest in the IF chain following the 1st crys-
         tal filter. While no direct measurements have been taken, there  appears
         to  be  little discernible difference between the first in this list and
         the latter.

         As can be expected, it is considered that the later model is superior to
         the early model. There is a natural tendency to  want  to  believe  that
         this  is  true, but practical application does not seem to back this up.
         One of the attractions for some enthusiasts is the vaccuum tube process-
         ing of the RF signal in the belief that the early model dual gate MOSFET
         is automatically inferior. The fact that all models in the later  series
         have  an  JFET  in  the RF chain is somehow strangely irrelevent to this

         Additional changes can be made to the audio and power supply  if  neces-
         sary.  Most  other  changes  are subtle and amount to 'busy work' unless
         there is a specific problem to address.
         1.3.2  Sources of Mods

         A number of sources did exist for mods to this equipment. Amateurs  like
         to  change  equipment around. If the equipment is popular, it is not un-
         usual for a cottage  industry  to  develop  for  some  enhancements  and
         goodies. Consider the following as reference only:

         Drake Mods (09 Nov, 1996)                                             21
             Sartori offered for sale a number of accessories for the R4C and TR7
             including solid state tubes (a 6BA6 was called a SBA6), crystal fil-
             ters, audio low pass filters and such.

             Most  notable  from  Sartori was a killer 16 pole 1.8 kHz SSB filter
             for the R4C.

         o   Sherwood Engineering

             Similar to the above, they provided R4C rework services and  crystal
             filters.  This company is still alive and very well. I doubt if they
             have any Drake accessories left on a dusty shelf. Sherwood Engineer-
             ing has a reputation for quality,  well  thought  out  solutions  to
             communications problems.

         o   Fox Tango

             Fox  Tango  was  bought  out by International in the early 90's. F/T
             originally was noted for their Yaesu FT101 filters and  first  mixer
             kit  changes. Regarding the Drake R4C, they offered add-ons known as
             GUF-1, GUF-2 and GUD. The first 2 were filters replacements for  the
             first  IF  crystal  filter  in the Drake R4C and were for SSB and CW
             respectively. The GUF-1 came in 8 and 6 kHz bandwidths. The GUD  was
             a solid state product detector kit replacement.

         o   International Radio

             This  company  deals in after market crystal filters for a number of
             radios. The filters are about $110 and are good. Their  filters  for
             the Japanese radios are better than factory and much cheaper.

             It  is difficult to find a better filter for a radio than from these
             folks. Most of their filters for all of the radios  that  you  could
             buy for are drop in replacements.

         Periodically  you  will  read  concern  regarding  'gain  balance'  in a
         receiver and how mucking with the blanker gain, for example,  can  upset
         the  gain  balance in the receiver. It is a concern. One should not con-
         fuse gain with sensitivity.  Although  both  are  related,  a  sensitive
         receiver is noted for high gain and low internally generated noise. Once
         the  receiver  is  sensitive  enough to increase its white noise on pre-
         selector peaking more gain just makes the noise louder, but the ratio of
         noise increase will remain much the same. The  various  RF  stages  that
         comprise  a  receiver  (RF amp, mixers and IF) act as a unit. Each stage
         acts as a signal conditioner as the desired and  undesired  signals  are
         amplified  and  filtered  prior  to  detection. With a properly designed
         receiver, increasing the gain in one unique  area  through  modification

         Drake Mods (09 Nov, 1996)                                             22
         ultimately  affects  the AGC'd stages since they are part of this entire
         loop. One typically mistakes a higher S meter reading after modification
         to mean 'more sensitivity'. This quite often is the receiver  attempting
         to  compensate  through  the AGC. With the AGC now more active on weaker
         signals and with the different AGC characteristics of the vaccuum  tubes
         now  receiving  AGC  sooner  than designed, the receiver is actually now
         partially shut down.

         AGC is very important in a receiver. Factors that affect AGC performance
         are loop gain, hysteresis, decay time and filtering. Close inspection of
         the R4 series receivers will reveal use of vaccuum tubes with  different
         Gm  curves (sharp and remote cut off) and different AGC filter time con-
         stants to each section. This accounts  for  the  excellent  AGC  charac-
         teristics of the receivers.

         If  one dives into this equipment making mods 'for more RF gain' or 're-
         duce the AGC pumping with sharp filters', these AGC relationships in the
         receiver as a whole get skewered and your Drake will not be any  better.
         Neither will it sound like a Drake anymore. While almost any AGC is bet-
         ter than no AGC, excellent AGC requires attention to detail. The results
         are worth the design and R&D effort.

         For fun, place an R4B next to any mid priced foreign transceiver and try
         an  A/B  comparison.  Now,  an  R4B  cannot  compete  in the selectivity
         sweepstakes against a radio 20 odd years younger (some things should  be
         better,  huh?),  but  have  a  listen  to  what  the  B  sounds like and
         watch/hear the AGC do its thing. If you listen carefully  you  can  hear
         the  AGC  recover and the receiver open up and recover from a strong SSB
         or CW signal. It actually 'breathes'. This is good, well engineered AGC.
         1.4.1  R4B and R4C Mods and Tech

         I've had a few folks ask me which is the most desirable Drake  receiver?
         Well,  it depends. First, its a personal item and therefore open for de-
         bate. I've had folks from various backgrounds provide  personal  reasons
         for the R4 A, B and C.

         For  reasons  that are contained within this document, I prefer the B or
         the early model C - the one with the MOSFET mixer.

         o   Voltage Regulation

             Early R4C receivers employed a 12 VAC secondary  power  transformer.
             Later  model  R4C  used a 14 volt power supply by changing the power
             transformer. The early model supplies could fall out  of  low  limit
             spec with marginal 110 VAC. While there is a Drake fix for this, the
             best option is to use an LM380 and lighten the power supply load.

         o   R4B/early R4C LO Injection

Drake Mods (09 Nov, 1996) 23

             R4Bs  injected  the  LO into the first mixer into the cathode from a
             low impedance link on T4. You can improve transceive injection  from
             the transmitter and reduce spurs on 15 and 10 by replacing R7 with a
             470  ohm  resistor  and bypassing it with a .005 uF cap. Run the in-
             jection  to  the grid of V2 pin 1 through a 10 pf capacitor from the
             high side of the small coil on the  bandswitch  associated  with  T4
             (essentially the switch selector finger).

             Realignment of the front end is required after this change.

         o   R4B Manual Trivia

             The front cover depicts the operation of the noise blanker.

         o   Low TX output in Transceive

             This  may  also  show up as low(er) sensitivity of the receiver when
             transceived with the transmitter (B and  C  series).  The  cause  is
             usually  alignment or the injection cables. All RF cables (the C se-
             ries had 2) must be RG/62 low capacitance cable. It is best to align
             the receiver and the transmitter when slaved together.

         o   T4any/R4any Intermitent Transceive

             Sometimes the crystal/VFO switch on the side of the R4B  can  become
             faulty.  In  most cases it is left in the VFO position 'forever' and
             is easily overlooked. As a matter of course, it  should  be  cleaned
             and cycled a few times.

             Pay  some  attention  to  the quality of the female RCA jacks on the
             back of the receiver and transmitter. Quite often  these  connectors
             no  longer  make  firm contact with the cables due to wear or abuse.
             Make sure that the center pin of the interconnect pin is pinched  by
             the  socket. In some other cases, you may find that the outside ring
             of the cable is similarly loose.

             Cable quality may also be a factor, especially if you are using  the
             original  cables. Remember - in most cases you are using cables that
             are about 20 years old.

         o   R4C Audio (all series)

             Change C100 from .22 uF to .68 uF. Do not use a higher  value.  This
             will remove a lot of the raspy audio and clean up a fair bit of dis-
             tortion. Use a tantalum and observe polarity.

         o   R4C Pass Band Bleed Through

             Replace  first  IF  crystal  filter  with 8 kHz GUF-1. HIGHLY recom-
             mended. The stock Drake filter is 4 pole with 65 db stopband  and  a
             very  poor  shape factor. The replacement International filter has a
             stop band greater than 80 db and a good shape factor. This one  sim-
             ple change will improve the receiver considerably.

         Drake Mods (09 Nov, 1996)                                             24
             A stock R4C came with 2 crystal filters - an 8 kHz wide first IF and
             a  2.4 kHz second IF SSB filter. The first IF filter does not do the
             R4C justice. Replace this filter with the GUF-1 if at all  possible.
             You  can  add  a  sharper  SSB filter. I use 2.1 kHz. Why not a 1.8?
             Well, the 2.1 has nice 6/60 db figures. It puts up a nice flat band-
             width plateau without killing fidelity. For CW, a 250  Hz  width  is
             about  right.  The 125 Hz is just a bit too narrow and the 500 Hz is
             too wide for current band conditions. The 125 Hz  makes  the  tuning
             and PBT control somewhat touchy. It rings surprisingly little and is
             a  good  CW filter. The 250 Hz is not all that much different except
             that the tuning requirements are more relaxed.


                 International Radio,
                 3804 South US Hwy 1,
                 Fort Pierce, FL
                 407-489-0956 (TU-FR, 13:00 - 17:00 HRS)

         o   Crystal Filters - Tech

             -   TR4 et al

                 These are 500 ohm 9 MHz filters. The TR4any are  single  conver-
                 sion  transceivers.  A  dedicated SSB filter is used for USB and
                 LSB, although either filter may be used depending upon the band.
                 The reason for two filters is to not have the transmit frequency
                 shift between the sideband selection.

             -   R4C

                 The first IF crystal filter is 5645 kHz at 500 ohms. The  second
                 IF frequency is 5695 at 50 ohms.

             -   TR7/R7

                 The  crystal  filters  are 5645 at 50 ohms. For this reason, you
                 can't put in the R4C first IF crystal filter into a TR7  for  an
                 AM  filter.  It  would  of  been so nice if the TR7 etc took R4C
                 crystal filters, but noooooooo. It looks like this was purposely
                 done in the TR7. The PTO/frequency on this radio is not inverted
                 ala R4any and the lower band edge corresponds to 5.05 MHz on the
                 PTO. The TR7 PTO is essentially the same PTO used in the C line.

         o   R4C S Meter Balance (early model)

             Some early R4C receivers could not balance the S meter  after  prop-
             erly  setting  the  AGC threshold (sensitivity control). Early model
             R4C receivers have only one trim pot for setting the S meter zero.

             Replace R33, a 470 ohm 1/4 watt with 680 ohm 1/4 watt.

         Drake Mods (09 Nov, 1996)                                             25
             The  sensitivity adjustment affects S meter balance and sensitivity.
             Ensure it is no higher than -1.35 volts and no lower than -1.2.

         o   BFO Bleed through R4C

             Early models could deflect the S meter while the passband tuning was
             moved across the IF frequency. Ensure all tube shields are in place.

             In extreme cases, check wiring harness layout and add a 47K  1/8  or
             1/4 watt resistor from the base of Q5 to ground.

         o   R4C Intermitent Crystal Calibrator

             The  mounting  screws  for  the  blanker brackets are held by two #4
             sheet metal screws from underneath the chassis. One of  these  is  a
             short screw. Ensure that this screw is positioned for the plate near
             the  chassis  edge towards the back of the receiver. A normal length
             screw will short the calibrator when the calibrator is seated down.

         o   R4C T7C IF Transformer

             The purpose of tapping the IF transformer from  the  output  of  the
             third mixer is to provide gain compensation for the higher insertion
             loss  of narrower filters. You'll notice a difference in the S meter
             reading of the calibrator should you have  another  SSB  filter  in-
             stalled  in  one  of  the CW positions. The S meter will increase in
             reading when this filter is selected. The  difference  could  be  as
             much  as  20  db  indicated.  While it may be annoying, it is not an
             indication of reduced sensitivity so long as you  can  get  a  noise
             peak from the preselector as outlined further in the text.

         o   50 kHz filter (late model)

             Seems  to  be applicable to serial nos 21000 and higher. Make a a 50
             kHz network of a 10 mH choke and 1000 pf capacitor in parallel.  Add
             a  .01  uF 250 volt cap in series with one end. Install this network
             from pin 5 of V6 to ground. The receiver in question should  have  a
             T7C (not a T7 IF can).

             Lead  dress for this mod can be critical and is noted by an increase
             in audio hash and hum.

             This change is applicable ONLY to R4C receivers that feed B+ to  the
             plate  of  the 3rd mixer through the notch filter. My own experience
             is that this change seems to do little, but it does no harm  either.
             Its  a  very popular 'secret mod' that you may want to try, just for
             the hell of it.

         o   50 kHz IF Coax (late model, early series)

             Late model R4C (tapped IF transformer T7C)  could  have  some  addi-
             tional  CW  crystal  filter  loss  due  to  use  of high capacitance

         Drake Mods (09 Nov, 1996)                                             26
             shielded cable running from  T7C.  Replace  this  audio  cable  with
             RG/174 and change the value of C49 to 430 pf.

             You don't need this change if there is no CW filter installed in the
             radio.  Your  receiver is eligible for this change IF you have a T7C
             (NOT a T7) IF transformer and if C49 is currently 390 pf in your ra-
             dio. In this case, the coax in question will have a slightly  larger
             diameter  than  the replacement RG/174 and will have a white colored
             center conductor.

         o   R4C Audio (all)

             The audio stage in all R4C receivers is terrible. It is a lousy  de-
             sign to deploy in a communications receiver. It causes a lot of heat
             to  be  generated,  distorts,  and  has terrible frequency response.
             There really isn't much you can do about this except  substitute  an
             LM380 for the whole damn thing. Connect the output from the LM380 to
             the  earphone  jack.  When  connected  here, the anti-vox will still

             The LM380 could be mounted on one of the support  brackets  for  the
             noise blanker or, if you build a circuit board for it and use ground
             lugs ala Drake, you could use the 2 audio output transistor mounting
             screw holes.

             Some folks have used the LM383 and this chip will provide a bit more
             audio  output.  Sartori  offered a conversion kit using this chip. I
             have no personal experience with this chip, but I've heard  that  it
             can be tricky to deploy without having it oscillate.

         o   Sartori Passive L/C Filter

             Sartori  provided an L/C filter that was inserted between the volume
             control wiper arm and the input of the audio amp ostensibly to  cure
             3rd  mixer  noise  and audio amp frequency response. I had one in an
             R4C that I had purchased and I removed it. I didn't like what it did
             to the recovered audio at all. If your receiver has this after  mar-
             ket  change, you may wish to make some of the changes - particularly
             the C100 value change if your receiver is stock. Bypass the  Sartori
             audio filter and see which you prefer.

         o   Power Supply - R4C

             This  is  another extreme R4C weakness. It is an incredibly poor de-
             sign. The 2 resistors at the right hand edge of the board  get  very
             hot  and will eventually cook the circuit board. One of these is the
             dropping resistor from B+ 150 for the PTO(!) Drake does this all the
             time in their equipment and it is a terrible design philosophy.

             You cannot properly fix the power supply unless you make  the  audio
             changes  because  the  class A audio output stage draws 1/2 amp (!!)
             and hauls the power supply down. Once you replace the  audio  stage,
             the  low  voltage  supply will climb and you are strongly advised to

         Drake Mods (09 Nov, 1996)                                             27
             install an LM7812 regulator in place of the pass transistor  at  the
             same time.

             Once  you  have  made  the audio amp AND regulator change, eliminate
             some of the heat generated from the PTO dropping resistor by  power-
             ing  the PTO from the low voltage 12/14 line instead of the 150 volt
             line. The PTO already has a series 100 ohm 1/2 watt dropping  resis-
             tor so .... no problem to run with the 7812 regulator.

             There  is another mod circulating that uses the filament supply as a
             voltage boost for the low voltage line. Do not do this  mod  and  if
             your receiver has had this change I strongly recommend you remove it
             and  revert the supply to original. This mod cures nothing and actu-
             ally generates as much, if not more, heat. What it was  supposed  to
             have done was raise the input voltage above the 7812 input threshold
             so  the  regulator can work with the 1/2 amp load of the stock audio
             amp. While this does work and does  reduce  hum  and  noise  consid-
             erably, it also creates a lot of additional heat from the regulator.

         o   Accessory Crystals

             Band crystals for the Drake and just about any other radio ever made
             may be purchased from:

                  LesMith Crystals Ltd.

             These  folks  do  small  -  read  single  - quantities and have his-
             torically dealt with amateurs since Day 1. They offer a high quality
             product at a reasonable price (abt $17 Cdn).

             Crystal specs are series, 20 pf and HC6/U for band tuning.  You  can
             also  use  the  crystal positions for fixed frequency operation, but
             this would most likely be used for MARS etc and I won't bother  with
             detail.  The  crystal  specs  are different between these two appli-

             The TR4any uses overtone crystals.

             Band range crystals are interchangeable between the entire R4any and
             T4any and even between the receiver and transmitter.

         o   CW Operation

             If you intend on operating the 4 line on CW only,  service  life  of
             the 6JB6 finals may be extended by turning the idle bias down to the
             point  that  the  PA cathode current meter just moves. Please do not
             run SSB at this setting. Be a pal.

         o   160 Meter Operation

             160 meters on the R4any/T4any was  an  option  and  enabled  through
             installation  of  a 12.6 or 12.9 MHz crystal. The crystal to use de-
             pends on operator preference. It all depends where you want the band

         Drake Mods (09 Nov, 1996)                                             28
             edge and what you want the frequency readout to display. If you want
             '8' to indicate 1.8 MHz, use the 12.6; if you want the band edge  to
             be '0', use the 12.9.

             Some  R4any that allow for 160 operation may have either the 12.6 or
             the 12.9 installed - I've seen both. If your R4 and T4 both included
             160 but use different 160 meter crystals, it  can  really  hurt  the
             brain when slaved until you get used to it.

         o   AGC Transients R4C (early model)

             Verify  that  there  is a network of a .01 uF and 1 Meg ohm resistor
             connected in series installed on the AGC board between the wire con-
             nect points on the board. This  network  is  installed  between  the
             green/white wire and the yellow/white wire on the foil side.

         o   AGC Pumping With Sharp Filters

             When  good  shape  factor  crystal filters are employed the AGC will
             pump when the calibrator is tuned right on the filter edge  and  the
             AGC is set to 'fast'. Excerpt July, 1976 Ham Radio pg 12:

             "....  designs  with  shape factors between 1.4:1 and 1.2:1 have two
             unpleasant side effects:

             1.  The extremely sharp skirt selectivity presents a problem for the
                 AGC circuit because of high group delay and phase  shift,  which
                 cannot  be  compensated  for.  In almost all cases strong inter-
                 fering signals at the edges of the  filter  response  band  will
                 make  the  AGC  pump. This instability introduces distortion and

             2.  Because of their high Q and ... the filters ring."

             Continuing, Rohde says ".... SSB reception should be between 1.9 and
             2.4 kHz to limit operator fatigue .... (The) bandwidth on the famous
             KWM-2 was restricted to 2.1 kHz for this reason."

             Ignore it. You can't fix this without hurting the otherwise  wonder-
             ful AGC.

             Many  theory  books show 'ideal' filter passband as an oblong box on
             its edge. This is not  inaccurate  when  confined  to  desirable  IF
             bandpass characteristics. 'Practical' filters have skirts. Some fil-
             ters  with  sharp  skirts will not cause severe AGC pumping but they
             may have quite severe ripple, depending on  the  response  type.  In
             general,  the  90's  approach  is for large stopband attenuation and
             filter shape factors of around 2:1. IF DSP can clean  up  the  skirt
             problem.  This is overkill for Amateur applications, but does illus-
             trate the move away from 1980-think of severe skirt roll  off  being

             There will always be trade offs.

         Drake Mods (09 Nov, 1996)                                             29
             Amateur  're-engineers'  have  claimed  that  an R4C weakness is 3rd
             mixer noise. Some of these amateur engineers have had a considerable
             'go' at the third mixer inventing theoretical problems  that  gener-
             ally do not exist.

             It is the 1st mixer that sets the sensitivity of the receiver. It is
             the  third IF amp that provides a significant amount of the receiver
             gain. By the time the signal gets to the 3rd mixer it should be pro-
             cessed enough to easily overcome 3rd mixer noise. And  it  does.  If
             your receiver works well, leave the 3rd mixer alone.

             Drake  employed  considerable  changes  over  the years to this area
             throughout the R4C series. Improvement in an early R4C can  be  ren-
             dered  by installing a pair of back to back diodes from the junction
             of C53 and C52 to ground. Use 1N4148.

             When Drake employed the 6EH7s as mixers,  the  injection  was  moved
             from  the  cathode  of the 3rd mixer to the control grid. It is this
             connection that some Drake enthusiasts assume to be 'noisier'.  This
             connect point isn't 'noisier' (white noise). It *is* very capable of
             creating hash and is much less tolerant of sloppy lead dress. I have
             a mod for this further on with much greater detail.

             There  was  also  a Sartori mod that injected the LO signal into the
             third mixer from the bottom end of the secondary of  the  3rd  mixer
             grid  input transformer. This mod follows good engineering practices
             and one of my R4C receivers has had this change. My  other  R4C,  an
             early  one,  has  the injection to the cathode of the 6HS6. I cannot
             tell much difference.

         o   R4C Noise Blanker

             Do not use the blanker gain trim pot  to  make  the  receiver  'more
             sensitive'.   It  won't.  Ensure  the  S  meter  deflection  on  the
             calibrator is exactly the same on 10 meters both  with  the  blanker
             and  with the 9 pin jumper plug. Excessive blanker gain will degrade
             the AGC by compromising the gain balance in the receiver and  possi-
             bly allow the BFO to bleed into the IF strip.

         o   Blue Dial Filters

             The  heat from the dial lamps will eventually turn the blue dial and
             meter filters clear. You can restore the color by dipping the  bulbs
             in  nail  polish,  specifically  Artmatic USA #163 Peacock Blue Nail
             Enamel (With Hardener) (Dec 1993 QST pg 86, A. Ross W2NXC).

         o   R4C IF and RF Amp Resistor Changes

             There have been previously published  mods  to  change  screen  grid
             resistor values to improve sensitivity and allow for S Meter zero on
             early  R4C  receivers. This is a bad mod. It does not improve sensi-
             tivity and is overkill as a method for S meter balance. It increases

         Drake Mods (09 Nov, 1996)                                             30
             the receiver gain and  consequently  alters  the  good  AGC  charac-
             teristics  of  the receiver. Do not do this mod and if your receiver
             has been modified, revert to original factory values.

         o   R4C Late Model 3rd Mixer

             As explained above, this 'flavour' of R4C with the 6EH7 3rd mixer is
             claimed to be noisier. Well, it isn't noisier. My late model R4C was
             not  original  in  this  area; it had been modified to inject the LO
             through the bottom of T6 into G1 of V6. It worked  well,  but  there
             was  a lot of hash - power supply 120 Hz spikes in the audio. When I
             placed a screw driver blade near G1 (or C199) of the 6EH7, the  gar-
             bage increased. This is no good. No good at all.

             The following will not cure white noise in the 3rd mixer, but if you
             have  the  above problems, it will kill this hash, buzz and assorted
             garbage once and for all. All mixers make white noise - consider  it
             uncurable.  Basically, this mod changes the 3rd mixer to cathode in-
             jection and allows G1 to be DC grounded. The verbal  text  describes
             the  end  result  of  the  circuit changes and is not a step by step

             Change CR20 and CR21 to 1N4148. Change C52 to .005 uF.  Remove  C200
             and C199. Replace C199 with a straight piece of wire. Where C52 con-
             nected to pin 1 of V6, connect it to pin 3. This essentially reverts
             the 3rd mixer of late model R4C with the 6EH7 to the circuit used in
             the early models.

             I  cannot  give  you a before and after comparison, for I never have
             had a chance to play with a stock late  model  R4C.  However,  after
             this  mod  my  '6EH7' R4C is dead quiet with the stock audio amp and
             power supply. With no  antenna  and  normal  volume  I'd  swear  the
             speaker was disconnected. Additionally, the problem with the S meter
             moving  as  the  PBT  control  was  rotated  was all but eliminated.
             Signals literally jump out of the speaker from nowhere. This  change
             will  not  make  the  receiver  more  sensitive, but it did clean up
             significantly the garbage in the audio (for me). The reason for this
             change revolves around the need for a DC path for  G1;  cathode  in-
             jecting  the  LO  is  the  easiest  way  of provide injection. Addi-
             tionally, the concept  is  proven  from  the  earlier  R4C  designs.
             Indications are that the 6EH7 is a pretty 'hot' pentode mixer.

             I cannot testify to what an original late model R4C was like. Before
             you  try  this change, I'd expect that you have some audio hash that
             gets almost unbearable in the AM position. When you place  a  screw-
             driver near C199, the hash and 'junk' increases in amplitude. If you
             do  not  suffer  these  symptoms  than rule 1 of modifications takes
             precedence ....

             "If it ain't broke, don't fix it."

         o   R4C Audio Hash

Drake Mods (09 Nov, 1996) 31

             R4C receivers are notorious for making not only horrible audio,  but
             also  having some hum and power supply hash thrown in for good meas-
             ure. Most of this is curable, but not without some effort. The later
             model using the 6EH7 3rd mixer is the worst of the lot.

             Noticeable  improvement  can  be  made by returning the power supply
             secondary grounds to the canned filter caps. Some folks have  put  a
             copper  strap  under  the  circuit  board ground lugs on the circuit
             boards, running a strip of copper under the whole length,  grounding
             the lugs. I'm skeptical about the long term. Copper corrodes.

             The low voltage supply/regulator/audio is marginal, at best. Measure
             the  voltage  on  the  audio output transistor emitter. If its above
             about .5 volt (assuming the proper emitter resistor), the transistor
             could be drawing too much current or be going into thermal  runaway,
             hauling that marginal supply down.

             The previously listed mod changing the 3rd mixer 6EH7 to cathode in-
             jection helps considerably, for it grounds G1 to DC. This (original)
             floating grid can be responsible for an incredible amount of crud.

             For  a simple solution to the inherently lousy audio response in the
             stock audio amp, the C100 change makes it much more pleasant.

             For the price this receiver sold for, it shouldn't have these  prob-
             lems  in  the  first place. What makes it worthwhile is how good the
             receiver  becomes  once  these  marginal  and  frankly  unacceptable
             characteristics are attended to.

         o   R4B Sensitivity

             Tune  in  the  calibrator and then pull V10, the 12AX7 noise blanker
             clamp. If the S meter rises, replace the tube. A  gassy  12AX7  will
             drive the NB clamp diode partially on, killing IF gain.

             If  a  new 12AX7 still does not cure the problem, it could be caused
             by the clamp diode. An acceptable substitute is a 1N270.

         o   R4B Crystal Filter

             An R4C first crystal filter can be used if T5 and T6 in the R4B  are
             replaced  with  R4C  part  number  251-9285. The filter would be in-
             stalled on the  preselector  bracket  and  coax  run  from  the  low
             impedance  windings of the replacement transformer to the filter. T6
             in the R4B is part of the crystal filter. There would be some  sheet
             metal  work  involved  for brackets and shielding to insure that the
             filter stop band attenuation was not compromised. You'd do  this  if
             you were to purchase a GUF-1 for your beloved R4B.

Drake Mods (09 Nov, 1996) 32


         All  of the Drake 4 line will transceive amongst themselves. Between the
         T4X and the T4C there was little difference. Most of the changes in  the
         T4C  from even the T4X were cosmetic or for better operator convenience.
         The B series used neon bulbs to indicate the active PTO when set up  for
         transceive; the C line turned the dial lights on and off.

         A  properly working T4any will give about 150 watts output on 80 meters,
         dropping to 40 or 50 watts on 10. The audio should be really  clean  and
         with properly operating ALC you should not be able overdrive the finals.
         There should be LOTS of drive on all bands.
         1.5.1  T4 Evolution

         The  T4X  and  the T4B differ very little, except mostly in the PTO dial
         plates. The T4C functionally was not much different from the T4B, except
         in areas of operator convenience. The T4C is noted for the following ma-
         jor differences:

         o   Separate BFO Line

         o   FETs in the BFO oscillator

         o   Different method of ALC detection

         o   VOX on/off from front panel

         o   Controls moved to back of set

         o   Dual concentric PTO dial plates

         o   Plain chassis

         o   Meter switch activated by pushing LOAD control shaft

         o   Active PTO indication by dial light

         o   Blank RCA jack holes for VHF transverter drive kit

         o   Separate VOX delay controls for SSB and CW
         1.5.2  T4any Mods and Tech

         o   Can't Tune 10 Meter Driver Plate

Drake Mods (09 Nov, 1996) 33

             This  is  characteristic  of  'generic'  6JB6  tubes.  Replace  with
             Sylvania 6JB6. Problem caused by high input capacitance of tube(s).

         o   VOX Gain - T4X and T4B

             In  cases where more VOX gain is required pick up the VOX input from
             the mic gain control instead of from the plate of V9b  pin  6.  When
             re-routing the audio pickup point, bypass pin 6 with a .05 uF cap.

         o   T4C TX Lock up

             Lock  up on a T4C is usually caused by a gassy mixer or 12BY7 driver
             tube. Other causes include leakage either to ground or B+ of the  TX
             keyed  line.  This  is  a  high impedance line. In extreme cases the
             cause can be T6. Inside T6 is a rubber washer that can  contact  the
             coil pins internally. The fix is to remove T6 and the shield and in-
             stall  a  fish  paper washer between the bottom of the rubber washer
             and the bottom of the transformer base.

         o   T4C Side Tone - Elimination

             Standby CW sidetone may be eliminated by placing a 22 Meg ohm resis-
             tor between the pin in the centre of the circuit board in  front  of
             V7  (the  one with the wire going to pin 1 of V7) and the lug at the
             top left of the board (the one with the 150K resistor).

         o   Substitute VOX relay tube

             A 6AQ8 will replace the 6EV7 if a 47 ohm 2 watt  resistor  is  added
             across pins 4 and 5 of V10. The tube change is applicable across the
             entire  4  line  (and TR3). The resistor IS NOT needed in any of the
             transceivers. Just swap the tube, in this case.

         o   Fan

             The PA cage area gets quite hot when in  use  and  some  forced  air
             cooling  is  desirable.  The easiest way of accomplishing this is to
             use a small 1 1/2" 12 volt DC fan. Mount the fan on the  outside  of
             the PA cage through the perf holes on the back of the PA cage. Power
             the  fan  from  a half wave rectifier filtered with about 100 uF de-
             rived from the 12 volt filament supply. Route the fan wires  through
             a  chassis  hole along back top of the chassis. The rectifier can be
             connected between the filament fuse and an insulated standoff.  This
             mod  can  be done without drilling any holes or destroying the units
             originality. Orient the fan to blow in.

             These types of fans are CPU coolers and can be bought for less  than
             $10.  They  do  not move a lot of air and move even less through the
             perf holes. What is necessary is not cooling, but  circulation,  and
             this simple expedient helps a lot.

             This  mod  will greatly extend the service life of the 6JB6 tubes at
             the expense of faster accumulating radio dust bunnies.

         Drake Mods (09 Nov, 1996)                                             34
         1.6  T4 RECITER

         This is a T4X with the PTO and crystal deck removed. It was intended  to
         provide  a transmit function in conjunction with the R4A and R4B receiv-
         ers. The only other similar device that I know of is the Atlas  210  se-
         ries.  A  similar  series  of  devices was the Atlas RX-110 receiver and
         TX-110  transmitter. The TX-110 used the VFO signal of the receiver in a
         way similar to the Drake R4B/T4 Reciter combination.

         Obviously, the Reciter is duplicated whenever you slave a separate T4any
         completely to the receiver.

         I've never seen one. This is an item for the curious  or  the  collector
         and  may  sell  for  either next to nothing or might demand a high price
         from its 'rare' nature. For the practical, and with  the  used  Drake  4
         line  so  readily  available,  it does not serve much of a purpose other
         than its novelty value. Any modifications or service notes  that  gener-
         ally apply to the Drake T4 series transmitters would apply to this unit.
         1.7  TR3 TRANSCEIVER (CIRCA 1963)

         This  transceiver  is  best described as a 'sleeper'. It is a 5 band SSB
         transceiver that predated the TR4, placing it in the mid 60's.  Most  of
         the units available are pretty weatherbeaten, but I have seen one or two
         that were in beautiful shape. All of them are relatively inexpensive. If
         you  want  a  nice,  inexpensive  glassFET transceiver, a TR3 is hard to
         beat. They work as well as a TR4 and look very much like one. I doubt if
         you'd mistake the two, but if you did, little harm would  be  done.  The
         TR3 has styling similar to a T4X, the precursor to the T4B.

         As  is not unusual for the Drake transceivers, most of what is mentioned
         for the TR4 is applicable for the TR3.

         Make sure you get the manual with the radio!

         Basic differences to the TR4:

         o   12JB6 tubes in the PA (3)

         o   Vaccuum tube PTO

         o   No rel output indication

         o   No CW sidetone

         o   No CW filter

         o   IF Filtering not as sharp as the TR4

         o   No provision for a blanker

         Drake Mods (09 Nov, 1996)                                             35
         If  all  you wanted was a TR4 to play retro radio with, a good clean TR3
         would do almost as well and can be had for a song. Be  careful  in  this
         area. Radios this old will suffer from use, and pay careful attention to
         the switches, controls and the operation of the two meters.
         1.8  RV3 AND RV4 REMOTE VFOS

         These  units  are functionally compatible to both the TR3 and 4. To have
         the RV4 work with TR3 only a minor change is required. Both units use  a
         12AU7  in  the buffer stage. The RV3 uses a 6AU6 for the oscillator; the
         RV4 is solid state using an FET. The RV4C uses the dual dial plates com-
         mon to all the C line and the SPR4.

         The RV3 will work with the TR4any, but the RV4 will not  work  with  the
         TR3  unless  the TR3 is modified. On the remote VFO plug on the TR3, cut
         the jumper wire running between pin 2 and 8. If in the future you remove
         the remote VFO, you must restore the jumper or make up a dummy plug from
         a Cinch Jones connector.

         The TR4 series represent possibly the  BEST  vaccuum  tube  transceivers
         ever  made.  The  transceiver will easily put out 200 watts on 80 meters
         and 100 watts on 10. For comparison purposes, the unit is somewhat SB100
         series like, but the TR4 receiver is much more sensitive on 15  and  10.
         Unlike the Heathkit, a noise blanker could be installed. It was only the
         very  last TR4 that had an RIT circuit. The TR4Cany had a plug in relay;
         on the TR4, the relay was open frame and hard wired.

         All TR4 have a 9 MHz IF that is incompatible with  other  C  line.  They
         will not transceive with an R4any, but they will mute and T/R switch the
         antenna  line.  Because a 9 MHz IF and a 5 MHz VFO is used, 20 meters is
         generated 'free' but tunes backwards as a consequence.  If  you  suspect
         the crystal oscillator having a fault, check for output on 20 or 80.

         The  TR4  had  full  10 meter coverage; on the TR4Cany only 28.5 was in-
         cluded - the other 2 band crystals were options.

         There were 4 different series of transceivers that I am aware of:

         o   TR4 (circa 1970)

             The basic transceiver. No RIT or CW filter.

             The AGC characteristics in the  TR4  are  'better'  than  any  other
             transceiver  in  the  4  line, but the differences are subtle. After

         Drake Mods (09 Nov, 1996)                                             36
             this model, Drake made some subtle changes  in  the  AGC  amplifier,
             V13. Full 10 meter coverage.

         o   TR4C

             The basic C transceiver. No RIT or CW filter. Dual dial plates. Some
             minor  changes in the tube line up and 1 pf caps on the IF transfor-
             mers to get some more gain. The  audio  output  stage  in  this  and
             subsequent  models employed negative feedback. Basically a plain TR4
             with C line PTO.

         o   TR4Cw

             Some subtle internal changes. Dual dial plates. Has a 500 Hz CW fil-
             ter. No RIT. Basically a TR4 but with the C style  PTO  dial  plates
             and a CW filter.

         o   TR4Cw-RIT

             The  final  model,  sold  for a period of time against the TR7. This
             model had it all - CW filter and RIT. It is distinguished by  having
             the  RIT control positioned in the lower right hand corner where the
             NB switch resided and having 2 pushbuttons in the  lower  center  of
             the front panel for activation of the NB and the RIT.

             The TR7 uses a very similar RIT circuit.

         Over  the  years,  the  TR4  didn't change all that much. All models are
         noted for high TX output, sensitive receivers and for running  hot.  You
         need a fan.

         Most  of the TR4any I see do not have the noise blanker. Pity. The 34PNB
         works very well. Typical for a transceiver of  that  era,  there  is  no
         selectivity  available other than the SSB crystal filter (or the CW fil-
         ter, depending upon vintage). Just about any flavor of a TR4 will  serve
         you  well on sideband, but to get the RIT function, you need to purchase
         a TR4Cw-RIT or have a remote VFO. In this day and age,  RIT  is  not  as
         important  as it was, for the people you are most likely to work will be
         more stable than you are. It is *they* that will be using RIT.  The  DC3
         or DC4 will allow the TR3 or TR4 to go mobile, but the radio is just too
         big  for most modern cars. There is no reason why you cannot operate one
         mobile, but you'll need a mindset for installation that goes beyond con-
         necting a 2 wire 12 volt cable to the back of the radio.  The  filaments
         alone consume as much power as a Scout puts out.

         It  is  possible to install an RIT circuit into the earlier model series
         transceivers by duplicating the Drake RIT circuit. Your  greatest  chal-
         lenge  will be to add in the appropriate controls without butchering the
         front panel, unless you don't care about it. Within 10 ms of taking your
         Black and Decker to the front panel, that TR4 of  yours  is  worth  ....
         nothing.  You  cannot make a homebrew RIT by rubbering the band crystals
         because 80 and 20 do not use band crystals. An  alternative  RIT  is  to
         find  an  RV4 or RC4. The chance of finding a TR4Cw-RIT is real slim and
         expect to pay if you find one. It is not too  practical  to  attempt  to

         Drake Mods (09 Nov, 1996)                                             37
         retrofit  the  CW  filter,  however,  since  this requires replacing the
         sideband switch and building mounting brackets. I have heard that  Drake
         will upgrade a TR4C to a TR4Cw for $105. This is a good deal.
         1.9.1  TR4 Mods and Tech

         The changes or mods for this equipment are few. The tube line up changed
         a  bit  - different 100 kHz oscillator tubes and such, but for all prac-
         tical purposes the radios performed about the same.

         o   TR4 Manual Trivia

             The front cover of the manual depicts the 2 crystal filters  in  the
             radio showing the skirt selectivity and bandwidth.

         o   Increase IF Gain

             The  TR4Cw  had  1  pf capacitors across the IF transformer hot side
             (T11 and T12) to increase the IF gain. Since bandwidth is determined
             by the crystal filter, this had no effect on the receiver.

         o   Different TX and RX Preselector Peaking

             Especially noticeable on 10 meters, its 'normal'. There is not  much
             you can do about it.

         o   9 MHz BFO

             Imagine  the passband curves of the two sideband filters together as
             the capital letter 'M'. The BFO is set dead center  in  that  middle
             valley  between  them. Proper setting of the BFO is to listen to the
             receiver with no antenna and switch the sideband selection,  adjust-
             ing  C130  for the same pitch. Sometimes you'll adjust it and 5 min-
             utes later, the adjustment has drifted.

             In almost every case, this is caused by C130 losing its  temperature
             characteristics.  Two  things  will  cause  this - the ceramic has a
             hairline crack or there is crud in the trimmer.

             The following is not for the heavy handed ....

             All of these Centralab trimmers are held together from the bottom by
             a tripod clip that fits into a ring machined  on  the  roter  shaft.
             Grab  the long pin firmly with some needle nose (bottom chassis) and
             GENTLY pull and push down at the same time. At the same  time,  push
             very  gently on the tripod clip with a small screwdriver just behind
             the center of the clip where you see the rotor pin . If you get this
             just right, the little ceramic disk on the top will fall out as  the
             clip extracts. Don't apply so much force that the trimmer is smashed
             or, when the clip lets go the pliers run amuck.

         Drake Mods (09 Nov, 1996)                                             38
             Now,  inspect  both  inside surfaces for cracks. If its cracked, re-
             place the trimmer. If it looks OK, clean both surfaces with  alcohol
             and a fresh J-Cloth. Don't touch the surfaces! Oil from your fingers
             will  ruin  the  repair  and you'll be punished by having to do this
             over again.

             Now put it back together (heh heh).

             Allow  the  radio  to heat soak for 15 minutes with the top cover on
             and then adjust C130. I've done this a  number  of  times  over  the
             years  with these trimmers on various radios (NCX-5, most Heath). Oh
             yes - NEVER put a pencil mark on the side of these trimmers to indi-
             cate calibration. Guess where the graphite goes in about 3 months?

         o   C130 TR4Cw and TR4Cw/RIT

             The adjustment of the above trimmer is somewhat critical for  proper
             CW  reception,  for the CW filter frequency is specifically designed
             for the 9 MHz BFO to be precisely on frequency. The sideband balance
             adjustment of C130 will affect the CW reception of the  transceivers
             - the place where the note peaks to a *very* large degree.

             Be  careful  setting  this  BFO trimmer, for there is a filter match
             procedure to follow also. Without the filters properly  loaded,  the
             BFO adjustment using the 'hiss pitch' will be colored by a poor fil-
             ter match setup.

         o   AGC Changes/Differences

             Around V13, Drake made changes after the TR4. It looks like this was
             done  to  provide  an  AGC  delay. In the TR4Cany, Drake changed the
             cathode to B- resistor from 47K to a 43K and a 150  K  in  parallel.
             This  network  computes  to about 33K. The change is subtle, but you
             could remove the 150K resistor, R193. This will make  the  AGC  more
             'active'.  This  parallel  network  *looks*  like  a post production
             change, but don't quote me.

         o   TR4any VOX Delay

             The TR4any has a fixed VOX delay. There is no  adjustment  for  this
             delay;  it has been set at the factory. The delay is about a second.
             The manual outlines a simple procedure for  setting  this  delay  to
             other than factory default. In most cases, the delay is about right.

         o   Antenna Fuse Bulb

             This  is located inside the final cage and is a #12 bulb. A #12 is 6
             volts at 150 ma - exactly the same as a #47, but  with  a  different
             base. This bulb is a bit silly, for it will take well over a watt of
             RF to open it. By then, the receivers ruined anyway, most likely.

             If you really want this protection (its good Stupid Insurance), pull
             the  bulb  and  put  a  Radio Shack peanut bulb (6 V at 50 ma or so)

         Drake Mods (09 Nov, 1996)                                             39
             across the terminals. The cold resistance of this bulb will not  af-
             fect the receiver adversely.

         o   TR4 Improved RX Audio

             On  the TR4, C212, a .0015 uF on G1 of V17, a 6AQ5, should be paral-
             leled with a .01 uF 300 volt cap. This will  remove  a  lot  of  the
             brassyness and distortion.

             Following  the  TR4, Drake made some changes around the audio output
             stage, but they employed negative feedback to recover the  frequency
             response of the sharp roll off of the coupling cap and grid resistor
             of V17.

         o   External Antenna Switch

             The  switch on the side of the TR4 allows for an external antenna to
             be connected. Whenever you move the transceiver, the switch moves to
             external by mysterious cosmic forces. You connect  the  antenna  and
             wonder  why  the receiver is dead. To prevent this, you can lock the
             switch by placing a 4-40 nut in  the  exposed  slot  where  the  tab
             slides  back  and  forth. Cover the nut with some tape to prevent it
             from falling out.

         o   What Happened to 15 Meters?

             There is no 15 meter adjustments in the radio aside  from  the  band
             crystal.  Make sure you place the preselector where the manual tells
             you to during alignment of the various bands.

             If you inspect the bandswitch, you'll see some small air wound coils
             about 1/4" in diameter. These coils are used for the three 10  meter
             crystal  oscillators and for 15 meters. Now that you know this, that
             does not give you an excuse to muck with them if you have trouble in
             these areas. Those coils have sat there for 20 years.  If  you  have
             trouble  in any of these areas in your radio, it will never, ever be
             with these coils.

         o   Low Sensitivity 40, 15 or 10 Meters

             First, check for sensitivity on 20 meters. Is it OK?

             What you've just done is verify that the front end is just fine  and
             that the problem is in the VFO premixer - the 6EA8. Quite often peo-
             ple  will  twiddle  the  transceiver - see "15 Meter Osc Inj" on the
             coil can and tune for max S meter. This is OK, but they forget  that
             there is a similar slug on the bottom of the coil can too. Of course
             one slug affects the other.

             And, again, you needn't bother with the loading network.

         o   Relay Cycling

Drake Mods (09 Nov, 1996) 40

             Especially  on  the transceivers, sometimes when you put the unit in
             TUNE, it will drop out or cycle as you advance  the  DRIVE  control.
             Nothing is wrong - its caused by having the RX audio set too high in
             relation to the anti VOX. Its actually the sidetone signal thats do-
             ing  it.  Turn  down  the  audio  gain,  pull  the mic or adjust the

             Another cause of relay cycling can be the filter can as mentioned in
             the general comments section.

         o   Relay Specifications

             The relay changed from year to year, from open  frame  to  enclosed,
             depending  upon  the  model  of  the transceiver, but the relay coil
             specifications did not. The relay is 120 volt and 15,000 ohm coil.

             What if I can only find a 120 VAC relay? Measure the resistance  and
             if  its 12K to 18K, use it. In most cases, AC relays are the same as
             the DC relays except for a shorting turn. In all likelyhood you  can
             use one and never notice the difference.

         o   Ventilation

             All  Drake vaccuum tube equipment that transmits should be placed in
             such a way that adequate air flow is provided.  This  is  especially
             true for the transceivers. If there is adequate airflow, you'll find
             Drake equipment to be quite gentle on components. Conversely, if you
             choke  a  TR4  off from free air circulation, you'll eventually cook
             the components. The first to go usually are ceramic disk capacitors.
             If you have to replace more than one or two of these, it is  a  sure
             sign that someone cooked the radio.

         o   Fan

             The  PA  cage  area  gets  quite hot when in use and some forced air
             cooling is desirable. There is quite a lot of heat trapped  in  that
             final  cage  that is trying to escape by convection. The answer is a
             fan, not so much for cooling, but to help purge the hot  air  inside
             the final cage.

             The  only  place  to mount a fan is on the back of the final cage. A
             small 12 volt 70 ma 2 1/4" fan just fits nicely. If  you  route  the
             leads through one of the corner chassis holes, they will come out in
             the final compartment. You can pick off the 12 VAC from the junction
             of  the  feed through and the filament choke. Do not go to the final
             tube filament pins - they are RF isolated by the chokes.  Power  the
             fan  from  a  half  wave  rectifier filtered with about 100 uF at 20
             volt. This mod can be done without drilling any holes or  destroying
             the units originality. Orient the fan to blow in. I use a larger fan
             on  the  TR4 than a T4any simply because the TR4 needs some good air
             movement. With the 2 1/4" fan on the TR4, the unit can be  used  in-
             definitely and does not give any signs of doing a mini-Chernoble.

Drake Mods (09 Nov, 1996) 41

             Please  note  that  the TR4 is not unique regarding heat. Almost all
             other radios of this era used convection  cooled  finals.  They  too
             need  some  forced  air  cooling or circulation. This is true of all
             Heathkits (inc HW12 series), Collins, Galaxy - the list is endless.

             This mod will greatly extend the service life of the 6JB6 tubes. For
             the  most part Drake did a good job designing the chassis for venti-
             lation. An inspection of the radio  from  this  aspect  will  reveal
             thoughtful placement of power resistors and discrete chassis holes.

         o   TR4 Noise Blanker

             This  blanker is very similar to the blanker on the R4C and is simi-
             larly very effective. Note that there is a different  blanker  model
             for TR4 serial numbers before 31321.

             Quite  a  few transceivers were sold without noise blankers. As with
             other Drake accessories, the 34PNB is difficult to find  by  itself.
             The  R4C  noise  blanker is unique from an TR4 blanker and cannot be
             modified to operate in the transceiver for the following basic  rea-

             -   Different IF frequency

             -   Different on/off switching

             -   TR4 blanker has bidirectional signal path
         1.10  SPR-4

         This  all  solid  state  receiver is a essentially a solid state general
         coverage R4B. It is extremely sensitive and  stable.  The  frequency  is
         'programmed'  by  installing  the  appropriate crystal - one of up to 23
         into the sockets behind the band selector switch.

         There are few weaknesses or vices in this receiver. The  AGC  design  is
         weird  and  in  certain points, very high impedance. An 11 meg ohm input
         meter will drag the AGC down.

         The SPR-4 uses the same PTO and dial plates as the R4C. Some models were
         specially constructed for the FCC when they cared about the mess  on  CB
         and  had the CB channels marked on the dial plates in red. It is done in
         an ingenious way and is fascinating to watch in action.

         There was an 'early' model SPR-4 and a 'late' model. The  exact  differ-
         ences  are sketchy at time of writing. One definite difference is in the
         audio board around the area of the power output transistors. Late  model
         SPR-4  used  a  pair of EP-487 TO220 transistors. Early model SPR-4 used
         transistors with unique mounting tabs.  The  entire  boards  are  inter-
         changeable  and still available in 1996. If you have an early SPR-4 with
         audio troubles, replace the board.

         Drake Mods (09 Nov, 1996)                                             42
         1.10.1  SPR-4 Mods and Tech

         o   Sensitivity

             Measure the input resistance with an ohm meter at the antenna termi-
             nals on any band but 'A' or 'B'. It should be about 2 ohms. If it is
             not,  likely  the  ground  pin on the input matching coil has become
             unsoldered. This will be hard to get to and you'll  be  required  to
             unscrew the slide switch on the back panel immediately above it. For
             some  reason this solder connection seems to fatique over the years;
             perhaps the area is stressed during assembly. On 40 meters and above
             an SPR-4 will still 'hear' a lot of signals with the input link coil
             ungrounded. All thats coupling the antenna  in  this  case  is  just
             stray  capacitance  and  is  surprisingly adequate. If you have this
             problem, you'll notice 80 and 160 not  to  be  too  perky,  yet  the
             receiver aligns OK.

         o   IF alignment

             The 50 kHz IF transformers tune broadly.

             The  50  kHz bandpass network coils accessible from the rear chassis
             panel tune sharply and are critical for  proper  sensitivity.  Align
             with  the bottom plate in place. It isn't easy, but this is the only
             way to get a good alignment. Do not disturb any of the wiring around
             this area of the receiver.

         o   AGC

             The AGC in the SPR-4 is somewhat unique. The  AGC  controls  on  the
             back  of  the  S Meter affect its strong signal performance. The AGC
             line is very high impedance.  You  cannot  measure  it  successfully
             without dragging it down.

             The  board  behind the S meter contains the RF amplifier AGC. If you
             have problems setting up the AGC in exact accordance  with  the  in-
             structions,  replace Q14, the AGC FET amp. The AGC bus goes right to
             the gate of Q14 - any leakage at all will ruin the  AGC.  An  MPF102
             will work fine.

         o   Alignment Tricks

             Drake wants you to measure the AGC bus during alignment. A voltmeter
             will  drag the bus down. Don't bother - there already is a voltmeter
             there - the S meter. Use it instead during alignment.
         1.11  TR5

         There is a natural expectation that incrementing series numbers  from  a
         manufacturer  imply that the higher number is a later model. In the case

         Drake Mods (09 Nov, 1996)                                             43
         of Drake HF radios, the TR7 followed the TR4Cw and the  TR5  came  after
         the  TR7.  Despite  this, the TR5 is a good interpretation by Drake of a
         solid state TR4Cw-RIT. There is a marked resemblance of a TR5 to a TR7.

         Most  notable  in the TR5 is a digital VFO, although the radio still em-
         ployed band crystals.

         The TR5 followed the TR7 and was announced  for  general  market  around
         1982.  It  is  a  ham  band only transceiver with a real synthesizer. It
         could best be described as being similar functionally to  an  TS-120  or
         Swan  MBX-100.  It  can  also  be described rather accurately as being a
         solid state TR4Cw-RIT. It came  with  few  accessories  -  there  really
         wasn't  all  that  much to add. It was an SSB and CW transceiver and did
         not cover the AM and RTTY modes offered in the TR7. The TR5 did  include
         WARC  band  coverage of the 10, 18 and 24 MHz sub bands. There is no PBT
         or IF Shift. It could be looked upon as a 'baby  TR7'  for  it  is  very
         similar  in  appearance.  Instead of two rows of push buttons on the '7,
         the '5 has a single row of rocker switches, but the basic layout is much
         the same.

         The TR5 also had its 'own' line of accessories,  most  notably  the  L75
         linear  (single  3-500)  and  RV75 digital remote VFO. The RV75 would of
         course work with the TR7. The companion power supply, the SP75  will  of
         course work with the TR7. This supply provides an unregulated  high cur-
         rent  12  volts  for the transmitter PA and a low current supply for the
         low level electronics. There is *nothing* wrong  with  this.  Atlas  did
         this  too. There is no need to provide a lot of filtering, OR regulation
         to the PA stage.

         Drake seems to have tightened up their specifications a  bit  since  the
         TR7,  especially in the area of third order intercept point. The TR7 was
         rated at +20 dbm at 100 kHz; the TR5 was rated at 0 dbm at 20  kHz.  The
         narrower  figure gives a more realistic rating under typical conditions.
         The QST review of the TR7 in May, 1979 was favorable but sloppily  done.
         The  TR7 DOES have an amplifier following the first mixer which is a di-
         ode DBM. There is an obvious typo rating the 3rd order of the TR7 at  90
         db. This is tantamount to saying you can connect the TR7 RF input to the
         national power grid. I think they meant dynamic range.

         The  TR5  has little to recommend it. The TR4Cany has charisma - the TR5
         is just a basic HF transceiver. The TR5 is a little rare and people  try
         to sell them as 'collectors items'. This, it might possibly be some day.
         Until  that  happens,  it  is just a simple, basic transceiver made by a
         company that no longer makes Ham gear. A TR4Cw-RIT *is* a bit of a  col-
         lectors item. The TR5 is *not*.
         1.12  TR7

         By  the  mid 1970's it was obvious that a new generation transceiver was
         required. Vaccuum tube equipment was being replaced by solid  state  ra-
         dios  -  especially  for  those that wanted to operate mobile. The solid

         Drake Mods (09 Nov, 1996)                                             44
         state equipment was obviously the way of the future. Drake answered this
         challenge with the TR5 and  TR7  transceivers.  There  also  was  an  R7
         receiver. This unit is not that common.

         Yes,  there  was a TR6. That was a 6 meter SSB transceiver circa 1970 in
         much the same vein as an SB-110.

         Yes, there was an 'A' model of the TR7. This is around  a  1982  flavor.
         What  the  'A'  model of the TR7 and R7 really was all about is that the
         equipment contained standard such as noise blankers and crystal  filters
         that were options on the earlier model.

         The  TR7,  as is common for most Drake equipment, is over built. This is
         characteristic of most well made American equipment. While a TR7 may not
         have all of the useless 'features' of foreign equipment, it is as  reli-
         able as a rock and solidly built. Drake made sure it was a quality piece
         of  radio and not intended to be disposable. An example - the TR7 gener-
         ates 150 watts (250 in or so) output, yet the PA is capable of at  least
         225  out.  At  its nominal power rating, the final transistors are under
         utilized. Most foreign PA  stages  do  not  have  any  where  near  this
         headroom.  The  transceiver  is  big  and  heavy  at 17.5 lbs despite an
         aluminium chassis. Glass epoxy boards are employed throughout the radio.
         The receiver is dead quiet and almost immune to overload. A  large  part
         of  the reason for this is the lack of an RF amplifier and a strong pas-
         sive DBM in the front end (ala Atlas 210). The TX SSB audio is rich  and
         clean.  The  AGC switches with the mode setting for near optimum tailor-
         ing. The only item to be missed is an IF notch filter. You'd look  at  a
         TR7 today perhaps with some distain if you didn't know any better.

         A TR7 is a classic example of old ham gear easily overlooked since it is
         'old  tech'.  Yet quite a few of the same amateurs will get very excited
         over a Racal or other piece of 'commercial' equipment. You'll read  fur-
         ther  on  what  a TR7 really represents. You see, Drake just didn't make
         amateur gear.

         A well working TR7 is a treat to use. Transmitted audio is excellent and
         the receiver is a gem. The major downside of the radio  is  its  current
         requirements.  Nominal  drain  on  receive is about 3 A, on transmit, it
         could run to about 22 to 25 A. Both  of  these  figures  are  considered
         slightly  excessive  today. The size of the radio rules out mobile oper-
         ation in most of todays cars and the red LED  frequency  display  washes
         out in sunlight.
         1.12.1  TR7A/TR7 differences

         The  TR7A was an early 80's transceiver that had some subtle differences
         to a TR7. Not that many were made and it is a bit of a collectors  item.
         Practically,  it  isn't  all  that much different to a TR7 except in the
         following areas:

         o   Came with noise blanker

         Drake Mods (09 Nov, 1996)                                             45
         1.12.2  TR7 Mods and Tech

         I  have encountered few mods for this radio. This could be caused by the
         difficult nature of performing them or by the very fact that a stock TR7
         is pretty good as it is. What makes this radio difficult  to  modify  is
         the  plug  in  board modules. This is good. This means that a TR7 is un-
         likely to be mucked with too severely. Your worst problem is  likely  to
         be alignment if your 'new' TR7 is a little sour.

         o   Servicing

             A  TR7 is a robust transceiver that is almost impossible to kill. It
             holds its alignment extremely well and generally  is  overbuilt  and
             'overdesigned'.  Once  brought  up to specifications, it should stay
             that way almost indefinitely.

             However, should your TR7 require service, you are in a bit of a  di-
             lemma.  To  service  a  TR7 beyond the superficial, one needs a good
             oscilloscope, voltmeter, service manual and the extender boards. The
             latter two are no longer available from Drake. A service manual  may
             be purchased from:

                 Antique Manuals, K7FG

             The telephone number is ... interesting.

             This  organization  sells manuals for a considerable number of exam-
             ples of old(er) gear and a lot of BoatAnchors. The current price  of
             the TR7 manual is about $34 US. Its not a bad deal.

             A  TR7  is not difficult to set up, but one must be aware of what to
             tune and what not to touch. DO NOT align the  first  crystal  filter
             unless  you are prepared to go at it with a sweep generator. Quite a
             number of slugs, trimmers and trim pots are involved in an alignment
             and not all of the adjustments are immediately accessible.

             Especially in the case of a TR7, if it works, don't fix it.

         Drake Mods (09 Nov, 1996)                                             46
             The  outlined procedures in the service manual are very well thought
             out and are presented in a  linear  progression.  Follow  them.  The
             synthesizer set up is a bit tricky. Most important is to ensure that
             the 40, 13.695 and 8.05 MHz oscillators are exactly on frequency. If
             each  one  of these is within 100 Hz, then the readout, PBT and CLAR
             will 'naturally' fall very close to spec. Proper test  equipment  is
             essential to set up a TR7.

         o   All Band Transmit

             Included  with this article are additional TIF and TXT files outlin-
             ing Drake synthesizer changes for full  receive  coverage  and  full
             frequency coverage transmit.

         o   Digital Display

             For  a while the DR7 digital display was an option. A TR7 is signif-
             icantly less without the DR7 display. If you are looking at a TR7 to
             purchase, make sure that it does indeed at least  have  this  option
             installed.  Of  all  the  'options' available for the TR7, it is un-
             likely you'll ever find a loose DR7 unless someone is cutting  up  a
             TR7 for parts.

         o   Early and Late Models

             The  very  early model TR7 was sold without the DR7 board. It is un-
             likely you will encounter one of these - few were made.  ASK  if  it
             has digital display before purchase!

             The  early  model  TR7  had  a 3 transistor predriver on the PA heat
             sink. Additionally, the adjustment for TX/RX frequency required  you
             to remove the DR7 and use extender boards. Very inconvenient.

             The  later model TR7 uses a 2 transistor predriver. You need to pull
             the top cover and look at the circuit board  closest  to  the  front
             panel.  If  you  see a U shaped aluminium heat sink, it is the later
             model. Additionally, this model  TR7  had  an  access  hole  on  the
             motherboard for the TX/RX frequency adjustment.

         o   TR7 Mixing Scheme

             The  TR7  and TR7A is a dual conversion transceiver using a first IF
             of 48 MHz and a second IF of 5.645 MHz. The same path is used in re-
             verse on transmit. For the BFO, there is no  5.645  MHz  crystal  as
             such,  for  it is synthesized from 2 crystal oscillators at 8.05 and
             13.695. The first mixer is a DBM followed by a  grounded  gate  post
             amplifier  in to a 48 MHz 4 pole crystal filter. On transmit, the 48
             MHz transmit signal is routed through the 48  MHz  filters,  through
             the  post amplifier and into the DBM. The post amplifier has its in-
             puts and outputs reversed through steering diodes. Output on  trans-
             mit  is  taken  directly  from the DBM into the 3 stage high gain PA
             section  (predriver,  driver  and  PA  functional  blocks).  ALC  is

         Drake Mods (09 Nov, 1996)                                             47
             achieved  on transmit by use of a diode attenuator in a previous low
             level stage.

             The primary reason for the mixing scheme is so full coverage from .5
             to 30 MHz can be achieved with a 5 to 5.5 MHz VFO.

             The  synthesizer  in the TR7 is a tracking synthesizer. The PTO at 5
             to 5.5 MHz is used in the PLL with the divider chain  to  control  a
             VCO  operating  at  48  to  78  MHz.  If  the  PTO  drifts, then the
             synthesizer will drift in step with it.

         o   RF Tightness

             The radio cannot be aligned when extender boards are  in  use.  Some
             adjustments  must  be  done  with the cover plate off. For the other
             adjustments, there are holes in the coverplate for access. These can
             only be accurately adjusted with the cover plate in place. Make sure
             the cover plate is screwed down snugly with all those screws  -  not
             just a few.

             Some  boards  have  grounding  fingers.  While  re-installing  these
             boards, make sure the fingers and tabs make chassis contact.

             If the above is not adhered to,  mediocre  alignment  and  operation
             will  result.  There  will  be RF leakage into the IF section of the
             receiver. This will have a dramatic  effect  on  S  meter,  AGC  and
             spurious responses.

         o   AUX 7 Programming

             See the separate section covering this option in detail.

         o   The FA7 Fan

             Some manufacturers do not provide for forced air cooling of their PA
             stages.  Ten  Tec  is a good example. Their PA stages can run so hot
             that it really hurts to grab the heat  sink.  I've  never  seen  one
             'melt',  but having them get that hot gives me the willies. Heat and
             electronics do not happily co  exist  (ref  TR4  above).  While  the
             transistors  may take it and good design compensates for it, thermal
             run away is a concern. Its an ugly event to watch and once  started,
             the event is catastrophic and expensive.

             The  FA7  was an option on the TR7 for heavy duty cycle use. Experi-
             ence has shown that without a fan, even on SSB, the PA gets  inordi-
             nately  warm.  Regardless  of  mode, some form of forced air cooling
             should be employed. The requirement is to provide  air  circulation,
             not  necessarily  air  cooling. The fan should be set up to blow in,
             not out. This is contrary to the FA7 direction, but seems to  afford
             much  better  cooling.  I  mount  the  fan so it blows in, under the
             theory fans move more air on the blow side than the  draw  side.  It
             does seem to be noisier blowing in, though. I really do not think it
             matters  all  that much, so long as you can get the temperature down

         Drake Mods (09 Nov, 1996)                                             48
             and the hot air out. If you mount it to draw, you should  feel  warm
             air coming out and the top of the cabinet 'cool'.

             The  FA7  fan runs from 110 VAC and is meant to be run 'through' the
             PS/7. If you have a PS/7, a 110 VAC 'muffin' fan will bolt right on.
             If you use a generic power supply use a 12 volt  version  and  power
             the  fan off the TX Vcc from the PA stage. 24 volt DC fans will push
             a fair bit of air quietly and these are readily available surplus.

         o   Digital Operation

             All Drakes with the exception of the TR5 use  a  free  running  VFO.
             This  may  not be stable enough for RTTY as the long term drift is a
             few hundred cycles. If you must use a Drake for  digital  operation,
             your  best  bet  is  a TR5 or a TR7 with an RV75 remote VFO (not the

             I have no T/R switching times for any of the Drake equipment, but it
             is reasonable to assume that none of it  switches  fast  enough  for

             * note readers comment on TR7 switching times

         o   Receiver Sensitivity Check

             The  calibrator should provide an S9 signal on 10 meters with no an-
             tenna attached if the alignment is  close.  Without  an  antenna,  a
             properly  operating  TR7  should appear almost to be dead. If the RF
             gain is rotated fully CCW, the S meter should rest at the S9 +80  db
             mark - no higher or lower.

             Since  there  is no preselector to peak, the calibrator test assumes
             the S Meter is set up in accordance with the alignment instructions.
             The other alternative 'sign of life' tests you can do is to  scratch
             the  center  pin of the SO/239 with a metallic anything. The S Meter
             should respond and you should hear the scritch noises  most  plainly
             in  the  speaker.  You  can  also  connect almost any antenna to the
             SO/239 and you should hear an increase in background noise,  however
             slight - even on 10.

         o   Receiver AGC Set Up Notes

             Aside from alignment, set up in this area has considerable affect on
             the  receivers  sensitivity and AGC 'personality'. Also important is
             the 10 volt regulator adjustment, for it too will have an effect  on
             oscillator  alignment, AGC and sensitivity. Tests indicate that at 9
             volts, the receiver and AGC setup is quite 'mushy'.  For  all  prac-
             tical  purposes,  the 10 volt regulator adjust is the one adjustment
             that will determine how 'crisp' the radio is.

         o   Transmitter Output Check

Drake Mods (09 Nov, 1996) 49

             A TR7 should produce 150 watts output on 80 meters if set  up  prop-
             erly.  Current  draw  will  be 22 amps at 13.6 volts. Use no smaller
             power cable than #12 for short runs and #10 for 15 feet or more.

             You  should  be  able to disconnect the transmitter load and key the
             transmitter to full output. Properly set up ALC will limit the  out-
             put 'power' to 20 watts or so.

             If  you  pull  the blue wire from the ALC board (the one between the
             shielded cable and the red wire on the LHS), the PA stage  will  run
             wide  open and I've measured over 225 watts output on 80 meters. Not
             recommended as a normal practice, but this is a good test  of  final
             transistor  health.  Set  to  its  nominal 150 watt output, a TR7 is
             definitely loafing along.

         o   Won't Transmit

             The TR7 has a separate pin on the power connector for +13  volts  to
             the  PA. Out of the 4 pin power connector pins, 2 are ground and one
             pin each is for the radio proper and the  PA.  Ensure  that  the  PA
             stage  does  have  13 volts. The transceiver will make all the right
             noises (relay closure, etc), but won't generate any RF.

             This is a common oversite. Its comparable to not having plate  volt-
             age for the PA stage in the TR4.

         o   Accessory Filters

             The  TR7  filters  are not interchangeable with the R4C filters. The
             R4C accessory filters are 5695 kHz and the TR7  are  5645  kHz.  The
             factory supplied SSB filter is a 'fidelity' filter. Your transmitted
             audio  with  a  properly  set up radio and a microphone should sound
             like FM broadcast. The skirt roll off is just a little  'soft'.  You
             need to go to a 1.8 kHz filter to get much RX improvement. The stock
             SSB filter is quite good in receive.

             The  TR7  always  transmits  through the SSB crystal filter supplied
             with the radio. You can put the other 3 filters where ever you want,
             but don't mess with this filter in this position.

         o   AM Filter

             An AM filter is almost impossible to find. You can fake an AM  'fil-
             ter' by putting a 390 ohm resistor through the input and output pins
             of any blank crystal filter position. It actually isn't bad. What is
             determining the selectivity is the 48 MHz first IF filter.

         o   Transmit Power

             Pay  particular  attention  to  the  SWR balance trimmer, C1901. ALC
             action is affected adversely by an improper null. This null  trimmer
             also affects the wattmeter calibration, so if you change the trimmer
             setting, R2001 and R2002 will need adjustment also. Essentially, the
             FOR  output is used for ALC and the REV output is used for shutdown.

         Drake Mods (09 Nov, 1996)                                             50
             This is independant of the wattmeter setting. When you  set  up  the
             ALC null, use a high impedance analogue meter, a non metallic align-
             ment tool and a good 50 ohm load.

             There are 2 control settings that affect the ALC. The obvious one is
             the 'ALC' control on the ALC board in the bottom of the transceiver.
             The  other  setting  control  is the gain pot on the predriver. This
             control sets the gain by setting the feedback on one of  the  driver
             stages  (old driver board) or the current in the preamp stage (newer
             driver board). Properly set, you should have just enough ALC  on  10
             and as expected, a controllable abundance on 80 meters. Improper set
             up of the ALC usually means no ALC or will make the mic gain setting
             overly  sensitive  and the ALC clamp early on the lower bands. There
             is additional ALC/drive compensation from the bandswitch for the  10
             and  15  meter  bands. Extra resistors are switched in on these band
             settings to provide more drive/higher ALC threshold to provide  gain
             compensation. These resistors have only a very minor effect on drive
             compensation.  If  you  are  having upper band drive problems, these
             resistors should not be the first suspects.

             For proper transmitter ALC action it is essential for the PA  driver
             and final stages to be in good condition. 150 watts output should be
             easily attained on 40 and 80 meters.

         o   External Speakers

             Unlike the '4 line, the TR7 employs an LM380 audio power stage. This
             IC is load tolerant and 8 ohm speakers may be used without problem.

         o   Microphone

             High  impedance  mics  may  be  connected to pin 4. Input Z is about
             750K, but this port is much less sensitive than pin 1. High  Z  mics
             are expected to be high output (> 100 mv).

         o   PA Driver Stage

             At  least  2  different sets of boards were used in the driver stage
             next to the power amplifier. Early TR7s used 3 transistors; the late
             model board used 2 transistors. In this board, the  last  transistor
             is  an MRF476. The final amplifier board seems to have remained much
             the same, but the components around the PA input and  output  trans-
             formers were different.

             The  board with the MRF476 predriver most likely was changed because
             it was much cheaper to make. This in itself is not a fault, but  the
             way  it  was executed presents some problems that will be dealt with
             in a separate area. On this board the driver  is  an  MPS-H20.  I've
             used  the  MRF237  as a replacement because the transistor is biased
             for about 20 ma - about .3 watt. In my mind this is a  little  heavy
             for  a  TO92 transistor. The MRF237 may also be used as replacements
             for the SRF2331. These transistors are somewhat unique - the case is
             the emitter and the collector and emitter pins  are  interposed.  If
             you  orient the transistor so the base (center lead is furthest away

         Drake Mods (09 Nov, 1996)                                             51
             from you) is in the centre and the transistor is held by  the  leads
             underneath,  the  emitter  is  the  left hand lead, NOT on the right
             where you would expect a TO5 to be. The case in question is a TO39.

             If  it  is  necessary to change any of the transistors in this area,
             you must use heat sink compound on the mounting  bases.  Most  folks
             use  far  too much of this stuff. The purpose of this compound is to
             ensure a good thermal contact between the transistor  and  the  heat
             sink  by filling in the (natural) pits in the metal faces. Thats all
             its used for. Too much is just as bad as none - its a  metal  filler
             only. Do not over goop this stuff!

         o   Late Model Driver Boards

             The  problem  with  the later model board is the bias network on the
             MRF476. Its bias level is such that  the  transistor  will  go  into
             thermal runaway or may latch up by itself. The 270 ohm resistor from
             base  to  ground is not enough to prevent this. The 300 ohm resistor
             and 1N4005 diode is an acceptable method of providing bias, but with
             the grounded emitter, there is no way to guarantee thermal stability
             around the transistor. You'll notice this if all  of  a  sudden  the
             transmitter output drops or, on the lower bands, the ALC is gone and
             more  mic  gain is required. You let up on the mic for a few minutes
             and all is well. If you were to feel the heatsink on the MRF476,  it
             will  be  very, very hot. It may also be possible that the predriver
             board 'eats' MRF476s. You find its bad - usually leaky and low  gain
             - replace it, and soon the new one dies an inglorious death also.

             The  cure  is to lift the emitter off ground with a resistor. Make a
             tight bundle of 3 - 1.8 ohm 1/8 watt resistors in parallel. Cut  the
             emitter  lead  of the MRF476 about where the lead changes width. Re-
             move the stub from the circuit board and put this  resistor  network
             between  the  emitter  and  where the the stub went into the circuit
             board. Removing the stub can be interesting for its soldered on both
             sides of the board.

             Yes, raising the emitter will decrease the  gain.  The  degenerative
             feedback also makes the MRF476 easier to drive, so the net result is
             a  wash.  This one change for this specific board type is highly re-
             commended, especially if you're tired of giving it MRF476's to  feed

         o   PA Stage

             Co  incident  with the different driver boards, Drake changed the PA
             stage a little bit around the ferrite  transformers.  These  changes
             look  like  they were done to improve stability, and the differences
             are minor.

         o   PA Stage Bias Setting

             There isn't any. There is no bias adjustment for any of  the  stages
             in  this  amplifier  chain. If your final or driver transistors have
             suffered catastrophic failure, before  installing  replacements  and

         Drake Mods (09 Nov, 1996)                                             52
             after  removal of the transistors measure the base voltage on trans-
             mit. Nominal reading is about .6 volts. If  higher  than  .7  volts,
             further  inspection of the bias supply is in order. Failure to do so
             will  likely  cause  the  new set to be compromised immediately upon

         o   PA Transistors

             MRF421MP will replace the SRF2337 final transistors.  The  MP  indi-
             cates Matched Pair, so order one of these or two MRF421 and ask them
             to  be  beta matched. At this power and current level, it is wise to
             have current balance in this stage.

             MRF475/2SC2092 will replace the SRF2338 driver transistors. The col-
             lector is the mounting tab, so don't forget the insulating wafer.

             MRF476/2SC2166 will replace the TO220 predriver.  The  driver  board
             changed  over  the years. The collector is the mounting tab, but its
             board placement is isolated from the circuit board. Do not  use  tab
             isolation  hardware.  The  collector  choke  makes collector contact
             through the bolt.

             The cost of all of the above is about $90 from RF Parts.  One  final
             transistor alone is over $63 from Drake.

             The  TR7  will  shut  down 50% at a 4:1 SWR. This provides more than
             adequate protection. However,  the  transmitter  draws  considerable
             current  from a 13 volt supply. The supply should be rated at 30 AMP
             ICAS minimum. Marginal supplies and DC power cords will not  provide
             enough current under load and likely will drop in and out under full
             carrier  condition jeopardizing the PA. It is important that a stiff
             high current supply be employed with the TR7.

         o   ALC Time Constant

             On the ALC board, the ALC decay time constant is over 1 second. This
             can be decreased to about 1/2 this value without any ill effects and
             will allow the ALC to track voice  input  a  little  better.  Change
             R1618, a 1 meg resistor, to 470K.

         o   VOX - Transmit Generator Board

             The VOX requires about 50 mv of microphone input to trigger reliably
             from  pin  1  on the mic connector. On the TR7, it takes a very high
             setting on the VOX Gain control to make the VOX  trip.  This  is  in
             contrast  to  the mic gain, where not much is needed at all. C304, a
             .01 uF capacitor coupling the voltage doubler has a reactance of 15K
             at 1 kHz. Its value is much too low, especially when the applied mic
             input signal is divided in half by C320, another .01 (transient sup-
             pression). Change C304 to a .1 uF. The improvement is such  that  it
             will take barely adequate VOX gain to 'acceptable'.

Drake Mods (09 Nov, 1996) 53

             I  recommend  this change for those SSB operators that would like to
             operate VOX on their TR7's but haven't for lack of VOX gain. I  have
             noticed no compromises inherent with this change.
         1.13  AUX7

         You can make the all band transmit mod by just cutting one trace for the
         TX  band  inhibit  line.  The  other, official way of getting additional
         bands is through the AUX7. This was an option board on  the  TR7  series
         that  allowed  one to operate the TR7 either crystal controlled or allow
         one to buy program modules for any .5 MHz segment. Special program  mod-
         ules  were  ordered for transmit. Use of an AUX7 is a nice touch, for by
         just rotating 2 swtiches, you can get to any band you want without  mod-
         ifying the transceiver. The option modules were all the same - you 'pro-
         grammed' the modules by cutting off the appropriate pins from a chart.

         Drake  no  longer  supports  the AUX7 optional band modules, but you can
         make your own from a 14 pin DIP header and a  batch  of  1N4148  diodes.
         Each  of  these modules will consume less than 13 diodes, depending upon
         the frequency. Yes, its a lot of diodes. Typically, you'll need 7  or  8
         diodes per module. You must use the diodes, for the band modules are ma-

         The  AUX7 is not easy to install or gain access to for it involves open-
         ing the TR7. The front panel will flip down, but to do this, you need to
         extract the bandswitch shaft. If you are not careful, you  can  rip  the
         wafer rotors out when you extract or reinsert the shaft. This will cause
         REAL  trouble and given the age of the unit and replacement parts avail-
         ability (don't count on it!),

         The AUX7 band module has a separate pin for TX enable.  Obviously,  this
         pin  must  be enabled for any of the WARC amateur bands you need or want
         to enable. The bandswitch must be set to the appropriate  filter  range.
         If  it is set to a range that does not match the module programming, the
         SETBAND light will come on.

         When you set up the DIP header with the 1N4148 diodes, use the following
         programming chart. The pin numbers are as if it were an  IC.  Make  sure
         you do not wire it backwards! This is a very common mistake:

              PIN  USE                     PIN  USE
              ===  ==========              ===  ==========
                1  Select 5V                 8  Range B2
                2  Range A0                  9  Range B3
                3  Range A1                 10  TX enable
                4  Range A2                 11  Band A
                5  Range A3                 12  Band B
                6  Range B0                 13  Band C
                7  Range B1                 14  Band D

Drake Mods (09 Nov, 1996) 54

         Essentially  the  AUX7  programming  is divided into 2 halves - BAND and
         RANGE. BAND sets the band as if it  were  coming  from  the  bandswitch.
         RANGE  sets  the .5 MHz offset as if you were to hit the UP/DOWN buttons
         on the front panel. The BAND programming is  compared  against  the  BCD
         bandswitch  wafer.  If  there is no match against these two, the SETBAND
         light comes on. This is used to tell the operator  that  the  bandswitch
         setting does not correspond to the programming and the bandswitch should
         be rotated until the light extinguishes.
         1.13.1  Band Programming

         Band  programming  is  done  in  BCD  to indicate the bandswitch setting
         through the SETBAND indicator. If this is not programmed, the unit  will
         not transmit. If pin 10 is not made high, the unit will not transmit.

             Band Range  BA    BB    BC    BD
             ==========  ==    ==    ==    ==
             1.5 - 2.0    -     x     -     -
               2 - 3      x     x     -     -
               3 - 4.5    -     -     x     -
             4.5 - 7      x     -     x     -
               7 - 10     -     x     x     -
              10 - 15     x     x     x     -
              15 - 22     -     -     -     x
              22 - 30     x     -     -     x

         The  band  range  pins BA to BD correspond to the previous 14 pin chart.
         This programming sets the bandswitch data/SETBAND light. If this is  not
         programmed, the unit will receive, but it will not transmit, even if pin
         10 is high.
         1.13.2  Synthesizer Programming

         The synthesizer requires programming in order to set the correct 1/2 MHz
         range.  This  requires  some calculation. The pins A0 to B3 comprise a 1
         byte field to indicate the correct .5 MHz chunk. You simply  cannot  as-
         sume  that 18 MHz is the 36th 1/2 MHz chunk and program '0011,0110', for
         there is a modulus to be accounted for.

         The formula is 86 - (F*2), where f is in MHz at 500 kHz settings. To set
         the synthesizer to 27.0 MHz,  you  would  calculate  86-(27*2)  =  32  =

Drake Mods (09 Nov, 1996) 55

                    0 0 1 1, 0 0 1 0         PIN
                    |     |  |     |         ===
                    |     |  |     |___ A0    2
                    |     |  |_________ A3    5
                    |     |____________ B0    6
                    |__________________ B3    9

         To program this 27.0 matrix, you would connect diodes from pin 1 to pins
         3,6,7  for the synthesizer, diodes to pins 11 and 14 for the bandswitch,
         and a diode to pin 10 to enable transmit. (but we'd NEVER do that, would

         The TR7 has 2 master oscillators that are selected  by  the  bandswitch,
         NOT  the frequency programming. Although it is not obligitory for recep-
         tion, you should also program the bandswitch data so the  SETBAND  light
         will  come on. A common error is to do the diode programming, fire it up
         and the synthesizer won't lock. This is usually caused by the bandswitch
         in the wrong position. The band programming and the SETBAND light is de-
         signed to prevent this.
         1.13.3  Crystal Control

         Crystal control on the TR7 is independant of  the  programming  matrix.,
         The PTO tunes up and is offset 50 kHz, so finding the right crystal is f
         +  5.05 - f(MHz). To crystal control to 7.055 MHz, you'd order a crystal
         for 7.055 + 5.05 - 7 or 5.105 MHz. For bands that are on a .5 MHz bound-
         ary, you'd subtract an extra .5 to put the crystal within the 5  to  5.5
         MHz  range.  The  above  crystal would put you on 3.555 MHz on 80 meters
         (3.5 + 5.105 - 5.05).

         Since crystal control is related to a specific band, you should  program
         the AUX7 as documented above. This is not mandatory.

         I  do  not  have  specs  on  the crystal, but an educated guess would be
         HC/25U, 20 pf, series, fundamental.
         1.14  R7 RECEIVERS

         The receiver is very similar functionally to an  Icom  R71A  or  Kenwood
         R5000.  The R71A is an excellent communications receiver. This is excep-
         tional company to be associated with.

         This is a triple conversion receiver, somewhat like an R4C. The last  IF
         frequency  is at 50 kHz in order to encorporate a notch filter. The sig-
         nal flow is crudely similar to an R4C, but the unit is more akin to  the
         receiver section from a TR7 with the following exceptions:

         o   Notch Filter

         Drake Mods (09 Nov, 1996)                                             56
         In  order to use the syncronous AM detector properly, the optional 4 kHz
         filter needs to be present.

         **************************** END ***********************************

Drake Mods (09 Nov, 1996) 57

         2.0  DRAKE PRICES

         The following represent a sampling of the prices of various Drake equip-
         ment  at  the  time  they  were sold. These are actual dealer prices and
         therefore there will be some variation.

              Unit                Description               Price hi/lo
              ====                ===========               ===========
              TR4                 Transceiver                 599
              TR4Cw               Transceiver                 799/699
              34PNB               Noise Blanker               100
              FF1                 Crystal Control              47
              MMK3                Mobile Mount TR Series        7
              RV4                 Remote VFO                  150

              TR5                 Transceiver (1983)          695

              TR7                 Transceiver                1100
              TR7/DR7             Transceiver                1295/1195
              TR7A                Transceiver (1983)         1445
              DR7                 TR7 Digital Display         195
              PS7                 TR7 AC Power Supply         195
              MMK7                Mobile Mount kit             50
              FA7                 Fan                          25
              RV7                 Remote VFO                  195
              MS7                 Speaker                      33
              NB7                 TR7 Blanker                  90
              MN7                 250 watt coupler            165
              WH7                 160-6 M wattmeter            89
              AUX7                Range pgm board              45
              RRM7/RTM7           Range RX/TX module            8
              385-0004            Service Manual (NLA)         30
              SLxxxx              TR7 Crystal Filters          52
              MN2700              1000 Watt Coupler           279

              DSR-2               Receiver                   3200/2950
              SSR-1               Receiver                    350
              2-C                 Receiver                    229
              SW4                 SW Receiver (1966)          299
              SPR-4               Receiver                    699
              R4A                 Receiver                    399
              R4B                 Receiver                    475
              R4C                 Receiver                    699/599
              MS4                 Speaker                      33/30
              FLxxxx              R4C Crystal Filters          52
              NB4                 Noise Blanker                70
              FS4                 R4C Synthesizer             300/250
              R7A                 Receiver (1983)            1395

Drake Prices 58

Drake Prices (cont'd)

              Unit                Description               Price hi/lo
              ====                ===========               ===========
              2NT                 Transmitter - CW            129
              T4X                 Transmitter                 399
              T4B                 Transmitter                 495
              T4C                 Transmitter                 699/599
              AC4                 Power Supply                150/120
              DC4                 DC Power Supply             195/165
              DC3                 DC Power Supply             149

              MN4                 300 Watt Coupler            120
              MN2000              2000 Watt Coupler           250
              B1000               4:1 BALUN                    25
              W4                  Wattmeter                    79

              L4B                 Linear Amplifier            995
              L7                  Linear Amplifier            995

              7072                Hand Held Mic                19
              7073                Hand Held Mic                19
              7075                Desk Mic                     39
              7077                Desk Mic                     45

              DL300               300 watt dry dummy load      20
              DL1000              1000     "      "            40

              UV3                 VHF transceiver             595
              UV3                 220 or 440 module           175
              PS3                 UV3 power supply             90
              UMK3                UV3 Remote trunk kit         70
              1525EM              Hand Held Mic w/TT           49
              WV4                 VHF Wattmeter                89

         Price  hi/lo represents the extremes of price range I've seen within the
         same time frame between dealers. This is in US $.

Drake Prices 59

         3.0  AUTHOR'S NOTES

         Anyone  who  contacts  me  for assistance will get it. I cannot say I'll
         make the badness go away, but I will give it a good shot.  Past  experi-
         ence  has  shown  that  trouble shooting at a distance is frustrating at
         best, but if you're stuck, I'm available.

         If you've found an error in this document or if its  caused  you  grief,
         then I WANT to hear from you.


         Where  comparisons  were made to other equipment or statements of 'func-
         tionally like' were indicated, they were done for illustrative  purposes

         I  have  heard  manys  a  time  Drake to be referred to as a "poor man's
         Collins." While I understand what is implied here, it is in a way an in-
         sult. Collins never really did make equipment for the Amateur. What ama-
         teurs got from Collins was commercial/military gear.  Its  analogous  to
         saying  a Kenwood TS450 is a poor man's SG2000. Its almost a meaningless
         statement. Drake, with the 4 line, made the best amateur  market  equip-
         ment  available at that time in the whole world. So good, as a matter of
         fact, a large percentage of this equipment is in service today and  will
         hold  its  own  in  a  dignified manner. There is not one piece of Drake
         equipment that I know of (R4C excepted) that was not the best  it  could

         Supposedly  we  make  things  'better'  now. But what is 'better' if the
         equipment is designed for a specific lifespan and made no stronger  than
         it  need  be for its intended application? 'Old tech' equipment employed
         construction techniques that are tried and true instead of  new,  trendy
         and 'the Next Generation'.

         The American equipment of the era of the 70's had a completely different
         engineering  philosophy. I've stated before that Drake equipment is well
         built. Additionally, just about every product in  their  HF  line  would
         work  together  in  some form despite the changes and progress made over
         the years. You could connect an RV4C to a TR3 with but only a very minor
         change. I can connect my R4B to my TR7 and  get  antenna  switching  and
         mute.  This  is  from the same manufacturer using two entirely different
         levels of technology manufactured over 10 years apart. This is  in  con-
         trast  to  todays  commodities that are replaced constantly with a whole
         line of new accessories. Rather than improve upon a radio,  todays  gear
         is  replaced  by  the manufacturer en mass. While the parts availability
         from Drake won't last forever, you can still get them for a 25 year  old
         radio.  An  S  meter  for an R4B is less than $15. And Drake hasn't made
         amateur equipment in over 12 years. I'll allow them  their  front  panel
         policy  as silly as it sounds, for their support is absolutely top notch
         and every bit as good as the other highly respected manufacturer of ama-
         teur products. Drake is America's best kept other secret.

         Author's Notes                                                        60
         I too lament Drakes departure from amateur radio. I suspect  they,  like
         others, got out of it for the reasons that have come true today. Selling
         ham gear is a cut throat business left to the big 'dealers'. There is no
         longer  brand  allegance, but price allegance given to the lowest bidder
         with  a  1-800 number. A $20 difference in price will kill the sale on a
         $2000 transceiver. To stay in the game you have to be a player  with  an
         army  of engineers and a 'new' product line every year. Drake and others
         saw this coming and went for a more stable market for their electronics.
         I hear stories of people asking Drake to 'come back'. Look at  what  the
         amateur  market  has  become today and ask why any domestic manufacturer
         would bother.

         Based upon my experiences with the TR7, I'd purchase a modern  Drake  HF
         transceiver  instantly.  'All'  Drake  need  do is update the TR7 to the
         90's. I have an SW8 and it has 'Drake' written all over it. Not the most
         extreme in technology and with some operational idiosyncracies, but  the
         audio  and  AGC scream Drake and 'modern SPR4' loud and clear. Drake has
         not lost their touch.

         While I will not use this as an opportunity to disparage foreign  equip-
         ment,  personally,  I've had my fill of this stuff. While it arguably is
         well made  and  engineered,  'marketing'  has  overshadowed  the  commu-
         nications  equipment it could be. It gets better slower than it gets re-
         placed with a new product line with yet more buttons,  knobs,  LEDs  and

         What  started my Drake exploits was pure happenstance. As is not unusual
         these days, I used to own a considerable count  of  Japanese  equipment,
         but  in  the  last few years I realized something was obviously missing.
         Call it 'soul' if you will. Maybe it was  triggered  by  a  visit  to  a
         stereo  store,  or maybe it was that woebegone orphan of an SPR-4 that I
         saw at a flea market. "He followed me home,  can  I  keep  him?"  Having
         danced  with  Japan  for a number of years, I realized that they stopped
         making communications equipment. What Japan makes these days is  'commu-
         nications  entertainment  devices'.  I  went out looking for some honest
         equipment and discovered how good Mr. Drake's wares were. I also discov-
         ered and confirmed that what you really need for some enjoyment of  this
         hobby  isn't all that much. The arms dealers will try their best to sell
         you a $6000 Death Star, but unless you're trying to  run  communications
         intercepts  for  the NSA, you don't need this stuff. My apologies to Mr.
         D. Vader.

         But I may be preaching to the converted.

         I do not profess this to be 'the' definitive Drake bible, but it  is  at
         least  not a bad start. I would like to think, and I do hope, that some-
         one that wrote off a Drake with a bad PTO has been able to dust  it  off
         and  fix it with a bit of glue. Unfortunately far too much old gear gets
         written off because fewer people have any idea just how well  it  really
         works.  It  ends up rotting in someones garage for lack of just a little

         I wrote this article for a few reasons. First, I wanted to publish what-
         ever maintenance tricks I had learned. I wouldn't want someone  else  to

         Author's Notes                                                        61
         learn the hard way as I did. Life's too short. Second, I believe that it
         is  important  that  mods  and  data  regarding this equipment should be
         available. The intent of this paper is not only to  put  on  paper  some
         mods  - I wanted to have some kind of a record indicating what this gear
         was like. Not only is this equipment part of  our  heritage,  Drake  and
         others  made  some  excellent products. An increasing percentage of ama-
         teurs every year have no idea what Drake, Collins, Hallicrafters or even
         Heath were all about. I see far too many hams swallowing QST dogma about
         the latest and greatest from KenYaeCom. Its a hobby guys.

         More than anything else, I guess, was the initial frustration I had get-
         ting information. Drake equipment and its expert enthusiasts  were  hard
         to find and were somewhat akin to visiting the Great Owl. I decided that
         anyone  that wanted to follow my path shouldn't have to go through this.
         One may read into this that I am a 'Drake expert'. This, I do  not  pro-
         fess  to  be.  All  I've  done  is  kept my eyes and ears open, had some
         experiences, and wrote them down for those that are interested. There is
         a wealth of information out there and I almost think that its kept quiet
         in order to maintain mystique and exclusivity. This  is  something  that
         old  farts do, unconsciously, for some reason or another. Where Drake is
         concerned, not any more.

         "I blew it up. I had to"

               Wayne Montague, VE3EFJ
               4146 Marigold Crescent
               Mississauga, Ont
               Canada. L5L 1Y7
               C/Serv (73057,3063)
               I/net  montaw@inforamp.net

Author's Notes 62

         4.0  READER FEEDBACK

         Included  here is some of the feedback I've received. I've included what
         I think is most interesting and what  provides  some  additional  infor-
         mation. Where no originator indicated, it is because I've edited it out.
         The  "...."  indicates  further editing that I felt was not pertinent to
         the subject at hand. Those that wrote and wish to be credited will  have
         corrections in the next release of DRAKEMOD.
         4.1  THE TR7

         (someone with MUCH more experience than I have)


         I  have  read with interest the three versions of your drakemod.txt file
         and appreciate the time and effort you have obviously  put  into  it.  I
         have  no  knowledge or experience of the Drake 4-line, and that makes up
         much of your document. However I can offer some  comments  and  amplifi-
         cation  on  the  portion of your work that deals with the 7-line and its
         commercial derivatives (more about that later).

         First, let me introduce myself and  detail  my  association  with  Drake
         equipment.  I  am  very  active  in  HF  digital  work  and  have run an
         APLink/WinLink MBO system for many years. My first piece of  Drake  gear
         was  a TR7A that I bought new in the mid-80s. I feel the same way as you
         do about the quality of construction and performance of this  gear.  The
         R7  and  derivatives have just about the best receiver I have ever seen,
         and that is saying a bit. My daytime job is with a  commercial  maritime
         service  provider  (HF)  and  we have evaluated many expensive receivers
         with names like Harris, WJ and Racal. I always bring them home and  com-
         pare  them  with  my  Drake  R4245  (an R7 inside, see below). The Drake
         stands up to all of them. Yes, they are fancier, computer  controllable,
         DSP  based  and  all  of that, but in basic receive performance the best
         that they can do is equal the Drake.

         My  radio  shack   consists   of   several   'systems',   separated   by
         functionality.  In  the descriptions below I have ommited the details of
         the digital hardware software and concetrated on the radios.

         Twenty Meter MBO system - a TR7A (w/PS7) slaved to an R7A,  both  driven
         by the same RV75. I have modified the RV75 to scan eight channels on the
         14 MHz. band.

         The  transmit  antenna  is  a  Butternut  vertical on the carport, and a
         dipole serves as a separate receive antenna ....

         Thirty Meter MBO system - a TR7 (w/PS7)  driven  by  another  RV75  with
         similar mod, scans ....

         Reader Feedback                                                       63
         HF  Intercept  system  - a Drake R4245, an Icom R71A and various digital
         modems and decoders. This system ....

         In  addition  I  also have a complete marine test 'ship' setup with with
         Raytheon and Furuno radios where I do software and hardware testing  for
         the day job.

         Drake  also sold a commercial version of the 7-line. The transceiver was
         called a TR4310 and the receiver a R4245. I have little knowledge of the
         TR4310 except a description in a four page brochure. (I would be  happly
         to  fax  you  a  copy.)  However,  I do own an R4245 and can describe it
         briefly for you. It is in a rack mount cabinet. Upon  removing  the  top
         and bottom covers, one finds an R7 mother board and card cage. The major
         change  is that the PTO is gone, as is the DR7. In place of the DR7 is a
         board that contains circuitry similar in function to the outboard  RV75.
         This  makes  it fully synthesized, very stable radio!  Other changes in-
         clude different style knobs (but everything is in the same place  as  on
         an  R7) and a light beige paint job on the front panel. The default fre-
         quency ranges when you switch bands are not the ham bands, but the mari-
         time bands. The radio will run from 12VDC, 24VDC or 110VAC.  I  obtained
         the  unit,  new, during last months of operation of the old Harvey Radio
         store on 45th Street in Manhattan. I passed up a TR4310 at the same time
         and have been kicking myself ever since!

         Your comments on the TR7's capability for digital operation need  a  bit
         of  detail  added.  First,  you are correct that the internal PTO is not
         adequate (stability-wise), that is why I use the RV75s.  However,  these
         radios  turn around very quickly and are ideal for AmTOR use. I TR7 is a
         bit slower for some reason, but still under 10 ms. Yes, there is  a  bit
         of noise from the clacking relay.

         In  fact,  I  had  several  years  ago purchased two replacement relays,
         anticipating failure, but both transceivers are using their origanal re-
         lays, believe it or not.

          Several articles have been published with improvements for the  7  line
         over  the  years.  My  library is not organised at the moment, so I will
         mention what I can from memory. Given some time, I can dig out either  a
         reference or a copy for you, if you are interested.

         There  was an article from an author in Switzerland detailing a stabili-
         zation mod for the PTO in the TR7. It consisted of a board, mounted  un-
         der  the  mother  board,  that  sensed a change in the least significant
         digit of the counter on the DR7 board and 'bumped' the PTO back on  fre-
         quency if it drifted far enough for that digit to change. It 'bumped' in
         10  Hertz steps, as I recall, which I thought might be too much for dig-
         ital work, so I never tried it. Also, I had acquired the RV75s  by  that

         There  have  been  many mods published over the years to allow full fre-
         quency transmit with the TR7. Most simply leave the transmit enable line
         high at all times by cutting a trace. Because internal signals like  PLL
         unlock  can drive this line low, I developed a mod that left this impor-

         Reader Feedback                                                       64
         tant protection in place. I have not looked at  the  mod  you  got  from
         Drake to see if it also does this, but I will.

         One author claimed that he had seen low level spurs on both transmit and
         receive  caused by the 23 kHz. oscillator in the +24 volt supply getting
         back into the +10 volt line. He suggested adding additional filtering to
         supress it. I have never seen this problem, but do  have  the  parts  on
         hand if I want to make this mod in the future. Similar circuits are used
         for this supply in the TR7, R7 and R4245.

         Another  article  included several unrelated TR7 mods. The ones I recall
         were a temperature sensing fan driver and replacement of  the  TR  relay
         with PIN diode switches. Circuit boards were available.

         Your comments on fans are interesting. I have an FA7, or homemade equiv-
         alent,  installed on both TR7s and on both PS7s, but using the Drake ap-
         proach, blowing out in all cases. Also, on the subject of heat and fans,
         I run both the R7 and the R4245 from external 12VDC, which  reduces  the
         internal  heat  somewhat.  In  spite  of that, the regulator on the rear
         panel runs quite warm, so I have arranged a fan to move air in that area

         I could go on and  on,  about  such  things  as  changes  to  the  Drake
         transceive  cable  kit,  a mod to remotely switch between 10 MHz. and 14
         MHz. operation. however, I suspect that this is enough for you  to  chew
         on for the moment.

         73, Craig (writer detail omitted)
         4.2  A 2B OWNER

         Date:  08-Jan-96 09:05 EST From:  Max Lockwood > Awesome Drake article

         Hello  Wayne,  Thru  Dave  (deleted) and with your permission, a copy of
         your treatise on Drake radios has been made availble to members  of  the
         "boatanchors" mailing list. I've read it. Great stuff!!!

         I noticed a relative lack of information on the 2B in particular and the
         2  series  in general. Are you interested in adding anything about these

         I don't have much info, but what I do have could be  useful  to  someone
         someday. For example:

         One  of  the  weak areas in the 2B seems to be in the crystal oscillator
         circuit. It's apparently common for the crystals to  cease  working.  If
         you  have multiple 2Bs (as I do), you can frequently play "musical crys-
         tals" and come up with combinations of rocks and radios that still work.
         Failing that, JAN crystals still has design data for  the  2B  and  will
         custom grind crystals for about $13.

         Reader Feedback                                                       65
         Another  weak area is the Sensitivity control on the back of the 2B. A 2
         meg pot used to adjust the AGC bias, it's not uncommon for it to develop
         a high resistance short to ground. Such a short can be the same order of
         magnitude as the value of the pot itself, 2 meg.  It  completely  upsets
         the  AGC  circuit  and results in an inability to mute the receiver com-

         If it is necessary to paint the cabinet of a 2B, an extremely good color
         and texture match can be had by using Rustoleum Satin  Black,  available
         in spray cans or in bulk.

         If  this kind of information would be welcome in your article, feel free
         to incorporate. All I ask in return is credit for the information be in-
         cluded with the article. One other comment: I was  really  glad  to  see
         your  remarks about the R4B. I have two of theses and am just blown away
         by their performance and their sound. (further comments deleted)

           73 and thanks,

           Jim Lockwood - km6nk

         ps. 'boatanchors' is a special interest group of 'vintage' radios. There
         is heavy interest currently in the R/390 series. Boatanchors is  located
         at  'boatanchors@theporch.com'.  You subscribe by sending E/mail to that
         address - 'SUBSCRIBE BOATANCHORS (your name)'. A TR7, R7 or a TR5 is NOT
         a boatanchor, by the way. If you don't know what an ART-13, Sky Buddy or
         an SX-101 is, this site may not be for you.
         4.3  JUST SAYING 'HI'

         Date:  08-Feb-96 18:18 EST From:  Tim (deleted)

         Wayne, just read your article Drakemd3.zip. I am just coming back to Ham
         Radio after an absence of 30 years...gave it up when I went to  college.
         I  was  talking to my old Ham chum and classmate of the 50's and he men-
         tioned that he had an old Drake from the 70's that he would let  me  use
         when I get my license. Think he said it was a Drake 3B but i'll find out
         for  sure  tomorrow.  Anyway,  I  was  fascinated with your piece on the
         Drake's and I thought I would drop you a note of  appreciation  for  you
         fine  effort  on everyone's behalf. I too have felt something lacking in
         the current breed of xcvr's when you actually try to sit in front of one
         for a few hours. My brother-in-law is a first time, enthusiastic, about-
         to-be Novice ham who plunked down about 1200-1500 bucks for  an  assort-
         ment  of  Kenwood stuff including a TS450/AT. Scanning the bands with it
         left me wondering what was missing. Maybe it is the wide open spaces  of
         1958  sunspot  peak  etc  but  I suspect your opinion hits closer to the

         Thanks for a great read.

         Reader Feedback                                                       66

regards, Tim (deleted)

         4.4  EXPERIENCES ....

         Date:  10-Feb-96 17:40 EST From:  Garey (deleted) Subj:  Drakemd3 File

         Wayne:  I really enjoyed reading your Drake "Masterpiece" file. I became
         a  convert  in  about 1961 when after being out of Ham Radio for a brief
         period I fell victim to a QST ad from (an amateur dealer)  in  Milwaukee
         for  a Hammarlund HQ-170 at a "closeout" price. After about a week I got
         a letter from them saying that they were all out of 170's, but would  be
         happly  to  sell  me a "new 170A" for only a few more dollars!!  My only
         excuse was that my last commercial receiver was an HQ-129X  that  served
         me well. Anyway, I fell for it.

         When  it  arrived, I set it up on the kitchen table in my apartment. The
         first night it never stopped drifting. I noticed that Hammarlund had ar-
         ranged the vfo tube filament to be on "all the time," and so I  left  it
         plugged  in and went off to work the next morning. When I came home from
         work, it was still drifting!!   The thing is probably up past S-Band  by
         now!!  Anyway, I took it to my friendly local ham emporium and traded it
         for a 2-B. Smartest move I ever made.

         Since  that time, I have owned the R-4, A, B, and C lines in approximate
         chronological order. I never owned a T-4 however.  I have never owned  a
         "bad" piece of Drake equipment. My first T-4X, which I drove Drake crazy
         for  after it was first announced, had a serial number of 10102. I found
         three unsoldered connections in the carrier oscillator  area,  but  once
         they were soldered, the tx worked for many years with no problem. When I
         talked  to  Drake's  service  department  they said I couldn't have that
         serial number because they never shipped anything below 10200. So  maybe
         they  just  got tired of me bugging them and sent me a prototype or pre-
         production model!!

         I used these rigs for RTTY autostart for years, 24 hour duty cycle  with
         sometimes  30  minute key-down times. I always used a small "Sprite" fan
         bolted to the back of the TX cage and would get 3-4 years out of  a  set
         of 6JB6's. Sylvania only, of course.

         Anyway,  now  that I have worn out your eyes, I will say that of all the
         equipment I have owned, I always go back to the Drake. I currently  have
         two  C  Lines  with  all Drake filters and NB installed. The only mods I
         have done were the Sherwood audio amp replacement with the LM-383.  They
         were  quite  specific  about the layout and bypassing of the chip, and I
         never had a problem with either one. I built the amp on a small (1.5"  X
         1.5")  piece of copper flashing, and RTV'ed it to the shield divider be-
         hind the AF Gain control.

         Finally, (whew!,) I spent some time working part-time for a  Ham  equip-
         ment  retailer  in the 60's and spent many "working" hours comparing the

         Reader Feedback                                                       67
         S-Line and the C-Line trying to decide whether to abandon the Drakes for
         the Collins mystique.

         At  that  time  the  Manufacturers of ham gear would sell their wares to
         sales people for 50% of list price rather than the "normal" wholesale of
         75% and that brought the Collins down into the "possible" range for  the
         working  man!  I couldn't convince myself that the Collins was worth the
         price, and stayed with the Drake. Today the C-Line is on  the  operating
         desk and the S-Line is on the storage shelves with the "back-up" C-Line.

         I  know that many (most) of us fail to recognize the work of people like
         you who take the time to chronicle this sort of information for the "in-
         grates" of today and tomorrow!!  I am as guilty as most, and after  wad-
         ing  through  all this, (if you get this far!,) you will wish I had kept

         Again, thanks and 73. Garey

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