03-08-2022, 06:39 PM
(This post was last modified: 03-08-2022, 06:54 PM by Mike Watterson.)
Yes, it works and I don't deny it. But you might as well use an 11mA 1j24b as a 1j37b at 60mA, because you are wiring the 1j37b as if it's a dual grid equivalent of a dual gate FET. A single npn transistor and crystal (or resonator) can also work as osc and modulator. I have one. Your 1j37b circuit will work with a 1j24b because you are not actually utilising the unique operating mode of the 1j37b. Re-read the theory.
I'm explaining the theory of the 1j37b & 1j42a used as a modulator, detector, doubler or mixer. That's the starting point, rather than a circuit that happens to work OK.
I'm not suggesting it needs to be more complex, but if simple is wanted, then use a triodised 1j24b as mixer osc*, or if in Pentode connection, drive g2 or g3 with video and osc is Anode to g1. There is no point to a 1j37b at all unless one signal is common to g1a and g1b and the other signal (osc feedback) is on g1a OR g1b, or differential drive to g1a and g1b.
[* see ANY EF80 based VHF tuner, the 1st EF80 just buffers the aerial, video or audio drive replaces that on a modulator-oscillator. Or DC90 based VHF tuner head (first Philips battery VHF in Germany) or Triodised DF97 VHF front end on almost all battery VHF valve sets]
Ability to startup and running level are two different issues with crystal oscillators. So if doubling component count is not an issue you can use either a 1j37b as mixer and 1j24b as osc, or use 2 x 1j37b (one with g1b& g1a tied as osc) in series filament, or 2 x 1j24b using g2 of one as LO in and the other a triodised osc. 11mA off a 5V supply via ballast resistor.
The 1j37b is filament hungry (60mA vs 11 mA) niche part that only gives an advantage over a 1j24b if used as intended (g1a + g1b = signal and LO ONLY to one of g1a & g1b, or differential)
I'm explaining the theory of the 1j37b & 1j42a used as a modulator, detector, doubler or mixer. That's the starting point, rather than a circuit that happens to work OK.
I'm not suggesting it needs to be more complex, but if simple is wanted, then use a triodised 1j24b as mixer osc*, or if in Pentode connection, drive g2 or g3 with video and osc is Anode to g1. There is no point to a 1j37b at all unless one signal is common to g1a and g1b and the other signal (osc feedback) is on g1a OR g1b, or differential drive to g1a and g1b.
[* see ANY EF80 based VHF tuner, the 1st EF80 just buffers the aerial, video or audio drive replaces that on a modulator-oscillator. Or DC90 based VHF tuner head (first Philips battery VHF in Germany) or Triodised DF97 VHF front end on almost all battery VHF valve sets]
Ability to startup and running level are two different issues with crystal oscillators. So if doubling component count is not an issue you can use either a 1j37b as mixer and 1j24b as osc, or use 2 x 1j37b (one with g1b& g1a tied as osc) in series filament, or 2 x 1j24b using g2 of one as LO in and the other a triodised osc. 11mA off a 5V supply via ballast resistor.
The 1j37b is filament hungry (60mA vs 11 mA) niche part that only gives an advantage over a 1j24b if used as intended (g1a + g1b = signal and LO ONLY to one of g1a & g1b, or differential)
