obrien135
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Diode mixer
I have built a diode mixer to moduate a 3MHz IF signal with audio from a microphone. It's hard to tell with the old oscillosscope that I have, but it looks like the signal out of the mixer is just the IF with no modulation. The primary of the output transformer of the mixer has what looks like the IF with the modulation on it on both terminals, but it looks like just the IF (unmodulated) is getting through. I tried making the load a higher impedance and adding a coupling capacitor to the output but it didn't help. The original resistance in the mixer circuit for matching was 75 ohms but I increased it by about a factor of three to keep from loading down the mic amp too much. It wasn't well matched with the circuit it was driving prior to that anyway (IF input). I'm not sure what would make it pass the IF but not modulated. Anybody have any suggestions?
George
KB1PDK
I have built a diode mixer to moduate a 3MHz IF signal with audio from a microphone. It's hard to tell with the old oscillosscope that I have, but it looks like the signal out of the mixer is just the IF with no modulation. The primary of the output transformer of the mixer has what looks like the IF with the modulation on it on both terminals, but it looks like just the IF (unmodulated) is getting through. I tried making the load a higher impedance and adding a coupling capacitor to the output but it didn't help. The original resistance in the mixer circuit for matching was 75 ohms but I increased it by about a factor of three to keep from loading down the mic amp too much. It wasn't well matched with the circuit it was driving prior to that anyway (IF input). I'm not sure what would make it pass the IF but not modulated. Anybody have any suggestions?
George
KB1PDK