Showing posts with label 6P3S. Show all posts
Showing posts with label 6P3S. 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.

6P3 (6П3) Beam Power Tetrode

6P3, 6P3S, 6P3S-E vacuum tubes

6L6 vacuum tube has been introduced by Radio Corporation of America in July 1936 and since 1937 it began to be produced in the USSR on equipment provided by RCA. For the first time it was usual metal 6L6 , but later was chosen glass bulb design in order to avoid overheating, so just before the WWII tube factories started to produce 6P3 (6П3) valves (left on photo), which was actually Soviet version of 6L6-GB tube.

After the forties, design has been changed (center tube on the photo) and the new one got additional "S" mark, which meant "Oktal" according to the post-war standard specification. There was some modifications such as 6P3S-E (6П3С-Е) (at the right on the photo) and 6P3S-EV (6П3С-ЕВ). I heard a lot of controversial stories about these extra letters, but according to the GOST it is Durability (E) and Reliability (V), so 6P3S-EV is just a high mechanical quality version of general 6P3S (6П3С) with warranted lifetime, probably military or industrial purpose. As for claimed electrical parameters, these 6P3S-E (6П3С-Е) and 6P3S-EV (6П3С-ЕВ) tubes has less current and voltage deviations than common 6P3S but according to my subjective opinion WWII 6P3 tube was a best performer in this family.

Naturally, 6P3 tube has always been one of the most popular in a variety of radio enthusiasts, it can be found in a Hi-End audio amplifier as well as in a HAM-Radio transmitter. BTW, not only HAM-Radio - it was and it is The Legendary Tube of the xUSSR Radio Pirates. Every Pirate Newbie starts with "The Whistle" - classical simple one 6P3S tube AM transmitter and so remarkable that a main web site of these guys is