03-08-2022, 05:03 PM
(This post was last modified: 03-08-2022, 05:04 PM by Mike Watterson.)
A centre tapped choke/coil between g1a & g1b fed at centre with video (or audio) and crystal to g1a or gib. The best for signal linearity is signal is common mode (equal on g1a and g1b) and differential (or feed only one half of grid) with LO
Or feed g1a OR g1b via cap and RFC. Tie g1a & g1b via small caps to crystal. This will give better Osc gain, but poorer input linearity
Make sure feed when oscillating doesn't overdrive crystal or it will drift with age and fail. Maybe drive crystal via G2 biased with a potential divider and RF tune the Anode, a tap on tuned Anode to drive crystal.
The 1j37b is not a dual grid in sense of regular valve, nor like dual gate FET. The g1a and g1b shorted (common mode signals) is g1 action. Any differential signal steers the beam and reduces the signal, because a g1 is a pair of plates parallel to the two beams, very close either side of the filamentary cathode. Even the dual grid Wunderlict valve is actually two interleaved grids, so doesn't work like this. The 7360 beam switching modulator is more like the 1j37b in operation if you only used one anode, except the differential LO signal on the steering plates is fed to g1a and g1b, and the signal to 7360 signal grid should be equal on g1a AND g1b. Of course on any modulator (ring diode, dual gate fet, Wunderlich, pentode, hexode, octode etc) you can swap the LO and signal, but normally you want the more linear and sensitive connection for signal, and the less linear or switching action can be done with a higher amplitude LO.
https://www.radiomuseum.org/tubes/tube_7360.html
https://www.radiomuseum.org/tubes/tube_wunderlich.html Read Joe's explanation. Unlike the 1j37b and 1j42a it doesn't easily act as a frequency doubler because it's really two grids. The 1j37a g1a and g1b are NOT two grids. They are a single grid to common mode signals and like the X or Y plates in a CRT (or modulation plates on 7360) for differential signals. So the differential g1a and g1b will frequency double as well as modulate the common mode g1.
When the theory of operation is fully understood, the best performance is achieved. See also ring diode mixer theory, where the best performance is when the LO is making it act like a pair of change-over switches.
Best stability always uses a separate oscillator. A single device mixer-oscillator always has an FM component in the output due to the input signal changing the oscillator operating point.
Working isn't the same as reliable or best performance. One signal must be equal on g1a and g1b and the other must be differential.
Or feed g1a OR g1b via cap and RFC. Tie g1a & g1b via small caps to crystal. This will give better Osc gain, but poorer input linearity
Make sure feed when oscillating doesn't overdrive crystal or it will drift with age and fail. Maybe drive crystal via G2 biased with a potential divider and RF tune the Anode, a tap on tuned Anode to drive crystal.
The 1j37b is not a dual grid in sense of regular valve, nor like dual gate FET. The g1a and g1b shorted (common mode signals) is g1 action. Any differential signal steers the beam and reduces the signal, because a g1 is a pair of plates parallel to the two beams, very close either side of the filamentary cathode. Even the dual grid Wunderlict valve is actually two interleaved grids, so doesn't work like this. The 7360 beam switching modulator is more like the 1j37b in operation if you only used one anode, except the differential LO signal on the steering plates is fed to g1a and g1b, and the signal to 7360 signal grid should be equal on g1a AND g1b. Of course on any modulator (ring diode, dual gate fet, Wunderlich, pentode, hexode, octode etc) you can swap the LO and signal, but normally you want the more linear and sensitive connection for signal, and the less linear or switching action can be done with a higher amplitude LO.
https://www.radiomuseum.org/tubes/tube_7360.html
https://www.radiomuseum.org/tubes/tube_wunderlich.html Read Joe's explanation. Unlike the 1j37b and 1j42a it doesn't easily act as a frequency doubler because it's really two grids. The 1j37a g1a and g1b are NOT two grids. They are a single grid to common mode signals and like the X or Y plates in a CRT (or modulation plates on 7360) for differential signals. So the differential g1a and g1b will frequency double as well as modulate the common mode g1.
When the theory of operation is fully understood, the best performance is achieved. See also ring diode mixer theory, where the best performance is when the LO is making it act like a pair of change-over switches.
Best stability always uses a separate oscillator. A single device mixer-oscillator always has an FM component in the output due to the input signal changing the oscillator operating point.
Working isn't the same as reliable or best performance. One signal must be equal on g1a and g1b and the other must be differential.
