Russian rod pentode circuits

[Kalee20]

At RF it's common for grounded grid to fed f- and f+ via a 1:1 transformer as a common mode choke. The DC cancels (f- to 0V and f+ to battery) ...

That's not strictly true! Although it's probably OK in practice, unless you use a really small toroidal transformer which saturates easily.

The current entering one filament lead isn't balanced by the current leaving the other. Some electrons take off from the filament (which is the whole point of heating it!) so there is a net DC current in the common-mode choke.

Regarding other matters, I made a push-pull driver using two 1j24b's, one operating as an anode follower, I am really pleased with it! HT is fifteen CR2032 lithium cells (from Poundland). Next task is a push-pull output - I already have the 1p24b's which look rugged devices. But I'll neede a better power source.

[Murphyv310]

Hi Kalee.
Glad to see more and more are experimenting with these valves.
My preamp for the Sonotone 9TA in the Pye black box has been perfect, perhaps using a sledgehammer to crack a walnut but its good fun and works great.
The Pantry TX now with 3 Russian valves (2 Rod pentodes and a low voltage triode..... 2v on its anode yes 2 volts) works a treat.
Next is to make a regen set for the frame aerial.

[BusyBee]

Well it's about time I updated my interest in this as my original post only answered an initial question.

My experience with valves is probably far less than others here, but I know the general principles of design and use. I am at an early stage of my investigations and designs, as most of my research is recent and I have only aquired a few of these valves within the past few weeks.

Research:
I have probably found most of the easily available information, but I do think more may be available on (particularly) Russian sites. I am trying to understand the basic philosophy behind the use and implementation from the Russian side. With this in mind I am studying Russian radio circuitry and some publications. Note: As may be expected I have come across, what I feel are errors, in some schematics. There may be more in the text but my understanding of Russian is very rudementary, such that I wouldn't know.

Plan:
Following my initial investigation of a 1j29b I am attempting to build a pantry transmitter. From study of various references and following my own previous ideas I am mounting each valve on a sub-board. (see photograph – the 1j24b module and a unpopulated 1j29b item).  I am aware that these valves are very susceptible to outside fields and the Russian military equipment usually has the valves shielded. My approach would make this easy to have a grounded foil shield.

The first one I have made is to be used in a crystal oscillator. The design I followed used a low frequency crystal (165 kHz), with the anode circuit tuned to a harmonic. The circuit I roughly followed at first was based on and oscillator in the Russian R326 radio (crystal between g1 and g2). I initially had problems so deviated to a modified Pierce oscillator which worked well. Further investigation when optimising the Pierce revealed why the original design was problematic (my lack of knowledge of valve oscillators!), so I returned to the original design (very easy with modular design). I optimised further on realising that my home wound coil was not ideal and a bought low current inductor I had would be Ok with the 1j24b as the current was well within range. This change made a vast difference in output.

Due to the output of the oscillator not being on it's fundamental I am planning to have a tuned buffer amplifier prior to the modulator to minimise harmonic output. There will be an audio driver stage so giving four valve modules in all. It may well be practical to do things with less but it is a learning experience for me so easy stages that can be isolated for test.

Power supply:
Currently I am powering things with bench supplies, but have made a 1.2V regulator which I am using for the heater (supplied via a 6.3V supply). The regulator uses a LM317 with adjust terminal to ground. This gives an output of 1.24V which is slightly high but within spec. I got this idea from a circuit I found online.

I plan to use a home designed circuit to supply the required HT. I have some ideas but in early testing stage as yet. I had previously managed to design and test an invertor circuit with 2AA cell supply giving 60V out, but was not happy above 1mA output. Interestingly very similar to the Russian ideas which I was not aware of at the time. I used Silicon transistors as my Germanium power types are limited

[Murphyv310]

Nice and neat way to "breadboard". I've found working with these valves very rewarding indeed.
1.24v on the filament is on the upper limit, ok for tests but on long term use try to get down to 1.1v. The rare dual control grid versions run between 6 to 9 volts HT and they are a doodle to make pantry transmitters with. See my YouTube clips.
https://youtu.be/v1D0D8qTHjs

[reset]

Hi.
Many of us are experimenting with these valves. Michael has been a great source of information as has many forums and experimenters.
What I can't find unless I'm looking in the wrong areas or due to Russian/Soviet secrecy is the lack of original circuits using these valves.
like I say I can't find anything. Do they exist or should I drop a letter to Mr Putin?

This Russian ham radio magazine has articles on the rod tube.
http://antentop.org/
You can browse and see what's there or do a google search on the site for specific tubes.
I have some data posted here.
http://radio.radiotrician.org/2016/12/ru...-data.html
73

[reset]

should I drop a letter to Mr Putin?

If Mr Putin ask for it back, give it to him. DO NOT tell him where you got it!
It was a very large file I reduced it to post. Still large enough to show details.

[Terry]

Well it's about time I updated my interest in this as my original post only answered an initial question.

In case you weren't aware, Mike Watterson is the expert on these Russian rod valves - see post #3 in this thread and subsequent posts.

Mike posted a lot of information on the old VRAT forum, so it would be well worth ploughing through that (I note that the search function still works, although I thought it had been disabled).

Here's a sample: http://www.forum.radios-tv.co.uk/viewtopic.php?f=3&t=7920&p=83168&hilit=Michael+Watt%2A#p83181

[Murphyv310]

Mike is very good but there has been a few errors that have been mentioned in the past that could confuse a novice.
In the main though I'd recommend his work especially the breakdown of specs and uses.

With the respect of screening this is important on circuits that are running low HT, the low voltage dual grid valves can be cut off with a small magnet........ but conversely that phenomenon can be used to advantage as well. I've even used it for audio coupling from the inside of a small transformer less the laminations, I'm sure there would be thousands of other uses.

[Nick]

The maths is pretty straightforward - with low HT, the electrons passing from cathode to anode have low speed and are moved off course easily... the electrons' velocity is directly proportional to the square root of the anode/cathode PD.

Basically, the energy gained by an electron caused by being exposed to potential difference (PD), E, is equal to Q*V, where "Q" is its charge, and "V" is the potential difference it's exposed to, so E is directly proportional to the PD - this is all kinetic energy.

Remember also the general-case kinetic energy equation E = 0.5 * m * v * v, ("m" is the mass of an electron) we re-arrange to get v (the velocity) = sqrroot(2E/m), so the velocity of the electrons is proportional to the square root of the electrons' energy, E, which means that the velocity is also directly proportional to the square root of the potential difference (see above).

Low B+ = low energy electrons = slow electrons = sensitivity to external fields...

[Murphyv310]

Absolutely Nick.
I really think these valves are great for novices, especially due to low HT