09-02-2025, 07:25 PM
Well I've finally got back to things. It was not the best of New Years with me but I have been keeping going, at a much reduced rate.
I have now built 1j24b and 1j29b Russian rod valve audio amplifiers. I gave them basic tests and determined that I was getting amplification. The resulting construction, although sound, ended up being a little untidy. I can see that the method would work well, with modification, for higher frequency work and Manhattan style / surface mount but I think it unlikely that I will continue this approach at audio / MW / LW. Next I will test the amplifiers with my audio amplifier. See photograph.
Another (sub)project I have been thinking of for some time is to use an Arduino with LCD display for frequency / wavelength display with a superhet receiver (effectively oscillator frequency). I did a test and determined that it was accurate enough. I used software readily available online. This works to good accuracy up to around 4MHz and to some extent higher (bear in mind the clock frequency is 16MHz so the limit will be well below that). Shown here is an input amplifier I built. The input is protected by a diode ladder rather than zeners. The main reasons for that is that I don't have any surface mount zeners but do have more than enough diodes. The actual amplifier is from a FET applications datasheet but is running well below optimum with a 5V supply. It did appear usable on simulation and initial tests are promising.
I have also designed a 6.3V to 5V regulator such that I can make use of my valve heater supply (I use DC) rather than have to use a separate supply. On simulation it appears to work well so next comes construction.
I have now built 1j24b and 1j29b Russian rod valve audio amplifiers. I gave them basic tests and determined that I was getting amplification. The resulting construction, although sound, ended up being a little untidy. I can see that the method would work well, with modification, for higher frequency work and Manhattan style / surface mount but I think it unlikely that I will continue this approach at audio / MW / LW. Next I will test the amplifiers with my audio amplifier. See photograph.
Another (sub)project I have been thinking of for some time is to use an Arduino with LCD display for frequency / wavelength display with a superhet receiver (effectively oscillator frequency). I did a test and determined that it was accurate enough. I used software readily available online. This works to good accuracy up to around 4MHz and to some extent higher (bear in mind the clock frequency is 16MHz so the limit will be well below that). Shown here is an input amplifier I built. The input is protected by a diode ladder rather than zeners. The main reasons for that is that I don't have any surface mount zeners but do have more than enough diodes. The actual amplifier is from a FET applications datasheet but is running well below optimum with a 5V supply. It did appear usable on simulation and initial tests are promising.
I have also designed a 6.3V to 5V regulator such that I can make use of my valve heater supply (I use DC) rather than have to use a separate supply. On simulation it appears to work well so next comes construction.
