2/5/2025: This page is being built; please be patient. Suggestions for new content are welcome!
A simple Heising Modulation system (go to page 28)
An informative Heising Modulation article by W8JI
A simple Screen Modulation system using a 6080 dual triode, and lots of chatter about it.
Microphone Circuits (lots of them!)
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Cathode Modulation is often an easy way to get on the AM air:
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.
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 as much as 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.
An article about using a stand-alone audio amplifier and a junk transformer to cathode-modulate a 250TH. This might work for many other tubes and avoids building an audio amp!