16-09-2017, 06:23 PM
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
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
