I recently saw the following on the INTERNET. After I stopped laughing I
thought it would be interesting (ie. useless) but funny to post this for
the benefit of others. The article was written by Jeff, NH6IL and I have
included it exactly as received. The circuit diagram I have converted to
GIF format from the original ASCII drawing and it is posted as SGTX.GIF.
I do NOT reccomend building the project, but it should give you a good a
good laugh. Regards - HARRY - Upplands Vasby - SM0VPO@SM5BKI.C.SWE.EU
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THE TSB TRANSMITTER
Now this isn't really for QRP (in fact, it's not at ALL for QRP), but it
was in the projects list, and since the original poster included it (as
a joke), I thought I'd make it available too.
HOW IT WORKS
The two tubes form a push-pull power oscillator, which makes alternating
current, but at a radio frequency. This is done by the use of L1, L2, L3
and the two little tubes (type 833 - alternatively F-24-a). The actual
frequency is not really important, as the object is to generate maximum
bandwidth .. the goal of any phone station. C1 is used to obtain maximum
power by resonating L1 to L2's natural frequency.
This RF voltage is stepped up by a factor of 30 to 100,000 volts by L2 &
sent on to the spark-gap where the actual RF-to-be-sent is generated. An
RFC accross the antenna is reccomended to keep the antenna circuit at DC
ground, yet will not short out the RF ... which is sent from the spark-
gap to the antenna.
The antenna wants to be one wire, and end fed. No co-ax required .. just
"hook er up and duck". The length of the antenna determines the transmit
frequency. the formula to use to get that length is:
FEET = (468/(((F*F)-(F*F)))*35.5
F = frequency in MHz (rounded off to the nearest 100KHz)
Voice modulation is done by use of a special Carbon Microphone, as used
in the 1920's ... which can handle several amperes. Here, rather than
sending R.F. through the MIC, as was done back then, only DC is passed
through. That way, the operator (or inflictor) won't get an RF burn on
his lips if he speaks too close to the MIC. That modulates the power to
the tubes, which varies the intensity of the spark which then puts quite
a suitable signal on the air. The intellegibility will match the content
of some of the QSO's now on the air.
TO OPERATE
1. Place mouth near Carbon Microphone
2. Close PTT switch and adjust C1 for a dip in anode current - QUICKLY!
3. Make OINKING and MOOING noises to indicate your presence to everyone
4. Open the PTT switch when you get around to it
.... .- ...- . ..-. ..- -.
Jeff, NH6IL
I am very grateful to Harold, SM0VPO for allowing me to add his files to my web site. He can be contacted by email: harold.lythall@era.ericsson.se
Frank, G3YCC