EM on AM! My homebrew transmitter.

[Electronic M]

Originally Posted by bob91343

The audio input is reversed, ground going to hot lead. The antenna is detuning the resonant circuit and so any variation there will change the frequency. You should bypass the B+ supply. Then you can ground one side of the tuning capacitor.

I believe that the audio works ether way, and just happened to be connected that way. I had such a rats nest going early on that I cooked a couple of pots (I had every element voltage except for the filiment supply on potentiometers hooked up as voltage dividers between B+ and ground) in the process of experimenting with a few things.

By "bypass the B+ supply" do you mean connect the B+ directly to the plate, and then hook one side of the transformer primary to the plate, the other to one side of the tuning cap and ground the other side of the tuning cap?

This is my first stab at tube design so given my limited knowledge of the design end I'm pleased that I got the thing to oscilate in the first place....Let alone got recievable, listenable modulation.

The Reason the unmarked cap has an "x" is that it came with the coil and the osc. doesn't seem to be significantly affected by it's presence or absence (by absense I mean one lead cut). Just thought I'd mention it if it makes a difference to anyone.