Showing posts with label 1960's. Show all posts
Showing posts with label 1960's. Show all posts

Experimental QRP transmitter by UB5DT, "Radio" magazine, April 1967

"Radio" magazine cover, April issue, 1967
For those of my friends tube radio builders, who asked me about "Soviet novice transmitter", "XUSSR QRP TX" (as it pronounced in telegraph),"something authentic, but not too complex" etc, such a RIG should be a good choice - easy to build and clearly adjustable design, small amount of widespread parts, a lot of potential operational fun (two possible output sockets, changeable configuration, very uncommon CW note, i believe). And, after all - a frumpish bald telephonist on the cover as a genuine sign of Soviet authenticity.

Experimental QRP Transmitter by I. Tsapiv (UB5DT):

This simple two-stage telegraph transmitter has been developed for a QRP experiments on the amateur HF bands.

The rock bound exciter on the 6П3С (6L6-GB) vacuum tube utilizes circuit known as the "Three-point" (or Tritet in common notation). The crystal controls the frequency of oscillation - 3510kc in this case. Signal output is taken from a separate tuned tank circuit L1C4 in the plate circuit of exciter; this tank should be tuned to 3510kc or 7020kc.

The second stage on the 6П7С (6BG6) tube acts as an amplifier or frequency multiplier (doubler or tripler) depends on an inductance of the L2 coil and bias voltage on the signal grid of this tube.
QRP Transmitter
If you would like to use this transmitter on 80m band as well as on 40m with a noticeable lowered power, you have to connect an antenna to the "A1" connector and pull the amplifier tube (6BG6) out from the socket. For the general power output on 7020kc and QRP operations on 14040kc and 21060kc that tube has to be back and antenna switched to the "A2" output connector.
Measured Power:
frequency single stage (6П3С) both stages
3510kc 8 W -
7020kc 3 W 18 W
14040kc - 6...8 W
21060kc - 1,5...2,5 W

Several interesting QSO's  has been obtained using this transmitter in October 1966. For example, UA0MX and K2AGU on 14Mc, and F9MC on 21Mc with a power level as low as 1.7 Watt.