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A simple Heising Modulation system (go to page 28)
CATHODE MODULATION (a.k.a. “series modulation”:
This article by Frank Jones, written in 1940, explains cathode modulation well.
“The Simplest Modulator” This is an old but reliable design for a tube-based cathode modulator. Try substituting these tubes with 6080’s which have much more current handling capabilities (but a much lower amplification factor).
Here is a cathode modulation scheme using an IRF-630 mosfet device…might be fun to try. Use any mosfet that will carry the cathode current. This scheme will not rob the plate voltage like the tube-based designs do.
Here is another (untried) cathode modulator using an FET; try an IRF-630 or one that can handle the cathode current.
This design uses a 6AQ5 to cathode modulate a 6AQ5 final RF amp tube.
XXX A carbon microphone is used in this cathode modulation scheme.