David F. Gauding, NF0R

The Portable Random Wire Vertical is a multi-band antenna
for the QRP enthusiast! This antenna was designed to
cover 10M through 40M, be free-standing and quickly installed/
removed by one person. It's just a random wire going
straight up..........but an "RWV" meets the requirements and
makes those contacts!

THE FEED SYSTEM

The key to this multi-band design is a transmatch based
feed system. The line is a 28' run of RG-58 with one major
difference! While it's connected to an unbalanced output with
a PL-259, the shield is allowed to float at the antenna's feed
point. This method allows the braid to serve as a tunable
counterpoise within a limited range. It apparently provides
an adequate RF ground at modest input powers.

The coax is terminated in a small alligator clip. The
line should be waterproofed after first tinning the stranded
center conductor to prevent wicking. A hose clamp positioned 
about 3" above the base serves as a feed point. The T-match,
Z-match or L-match may be used interchangeably in
this application.

THE RADIATOR

The radiator for a basic RWV is 33 1/2' of graduated an-
tenna tubing. The outside diameters are 1 1/4", 1 1/8", 1".
7/8", 3/4" and 5/8". The overall length was chosen to
achieve a full quarter-wave on 40M. With hose clamps in
place the antenna collapses to less than 6 1/1'. This size fits
the interior of mid-size cars and most compact sedans.

Heavy-duty type 6061-T6 extruded aluminum tubing in
.058 wall is recommended. This grade is very strong, flexes
in windy conditions but will not take a set. Other grades of
tempered aluminum are probably suitable but have not been
fully researched.

Slot across the top of each section with a fine tooth
hacksaw blade to a depth about the same as the tubing 
diameter. Slotting produces an excellent compression joint but
leaves sharp burrs on the tubing. The burrs may be eliminated
using a round metal file and the surface finished with
steel wool.

Any metal chips left behind must be removed before the
radiator is assembled. This will prevent scoring of the aluminum
and possible jamming when the close tolerance sections are 
assembled. A cloth attached to the end of a stiff cord 
and pulled through the tube works well for the interiors.
Circle sections two through five with a permanent marking 
pen, six inches from the un-slotted end. This serves
as an important visual warning to stop extending a section
prior to re-tightening the hose clamp. Those desiring 
absolute maximum height may use less overlap bur for structural
integrity not less than two and one-half tubing diameters.

The radiator is now ready to be assembled. The stainless
steel hose clamps are installed at the feed point and at the
top of the first five sections. Recommended sizes are: 38
mm (2). 32 mm (1), 25 mm (1) and 22 mm (2), all with
standard 5/16" heavy-duty hexagonal screw heads and wide
clamping bands. Position the clamps on the tubing so the
screws can be reached from the same side of the mast. A
guying ring is added at the 6' level as discussed in the 
following sections.

THE MOUNTlNG SYSTEM

The collapsed radiator is socketed in a heavy-duty 1 1/4"
diameter rubber crutch tip which insulates metal from the
earth. The crutch tip is tightly pinned to the ground with a
screwdriver passed through a drilled center hole.

Select a screwdriver handle with a minimum shaft
length of 6". The handle should fit snugly inside the base
tube. A Phillips-type head is preferred for easy insertion into
the earth by hand pressure alone. The completed radiator is
then pressed firmly into the socket. This mounting system
supports the nested tubing while the guys are being attached
and expedites installation by one operator.

THE GUYING SYSTEM

The three point grounding system is connected to a 1 1/8"
inside diameter steel or brass washer installed between the
first and second sections. Drill three equidistant holes in the
washer to accept small S-hooks as described below.

The correct guy length for a basic RWV is 9'. Select
1/8" or 1/16" diameter solid plastic clothesline with a
stranded nylon core. This line is strong, will not stretch or
unravel and contains no metal to absorb RF.

The guys should be carefully attached to 1 1/4" or 1
5/8" steel S-hooks with securely locked knots. S-hooks are
available in hardware or variety stores. Check to insure they
will pass the largest screwdriver being used as a guying
stake. A hook used at the guying ring is closed on one side
with a pliers. The open side of that hook is attached to the
guying washer. A hook on the earth end of a guy is pressed
closed on both sides.

The earth end of each guy is held in place with a 6" or
longer screwdriver set at a forty-five degree angle. A sharp
Phillips-type head is again recommended for easy insertion
in hard earth. After several practice sessions a new user
will have little trouble setting the nested antenna perfectly
straight.

The guys should be taut but need not be overly tight.
he three-point system coupled with a pinned base is remarkably 
stable, even in windy conditions. The basic RWV
antenna and guying system has unintentionally survived 30
mph storm gusts in portable use without difficulty.

EXTENDING AND LOWERING THE ANTENNA

The fully assembled radiator weighs just under six
pounds and is very manageable. Antenna installation takes
one experienced person an unhurried five to seven minutes!
Lowering the antenna is the reverse of the installation procedure and
takes less than two minutes.

What happens to performance with longer or shorter
feedlines? Other feedline lengths up to 50' have been substituted
with no significant changes noted in performance characteristics on 
10M through 40M. The 28' run of RG-58 was actually chosen at 
random from coax already on hand. Since it seems to work well 
there has been no serious investigation  to date into feedline 
alternatives. A longer shield braid appears to provide a better 
artificial ground, particularly on 80M, but at the expense of 
increased feedline losses.

What about higher operating powers? 
The basic antenna and feed system load easily and have 
handled 100 watts input during informal tests. No unusual 
SWR changes or coax healing were observed. The impedance 
is non-critical in this application so either 50 ohm or 
72 ohm coax may be used.
It should be noted that the shielded feedline tends to keep
stray rf out of the station at all power levels.
 
Does the RWV require any maintenance? 
During installation the friction between sliding tubing sections 
(.009 clearance) assures good electrical contact at all times. The
withdrawal warnings on each section will have to be re-
marked periodically. Check the feedline waterproofing and
locked knots occasionally. At least annually disassemble
the radiator, clean the tubing and wipe each section with a
cloth lightly sprayed with WD-40. At the same time a little
lubricant should be placed on the hose clamp screws.

How else can this design concept be utilized? 
Replace the aluminum radiator with a wire! It should be at 
least a quarter-wave length on the lowest operating frequency. 
Ideally, The wire should hang straight down from an insulated
support or tree branch. Backpacking hams can exchange the
RG-58 for RG-174 to reduce weight but should anticipate
additional feedline losses.

WHAT'S THE BOTTOM LINE?

The RWV is a compromise design and not particularly
efficient electrically. Nevertheless, in eight years of active
use this simple portable antenna has consistently worked
states. provinces and DX from 10M to 40M. Any 33 1/2'
vertically polarized antenna in the clear and resonant is going
to make contacts. even when running QRP!

CLOSING COMMENTS

  With this design the QRP portable enthusiast has wide
latitude in choosing operating locations. It's a major advance
from being totally dependent upon trees or other supports
when utilizing otherwise excellent wire antennas. The self-
supporting radiator and accessories are relatively light thus
easily carried from a vehicle to nearby picnic benches or
campsites. Finally, the convenience with which a single 
operator can install a RWV means more air time is available
when running portable.

Just for fun, put the receiver on line before extending
the radiator. Then tune a weak CW signal and listen for that
inevitable increase in signal strength. Height is still every
thing when it comes to antennas!

Good luck and have fun in the field with your own
RWV! Hope to catch you QRP portable soon!

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