EM on AM! My homebrew transmitter.

[Electronic M]

Reciently some threads here reminded me that I had some really small tubes tucked away, and got me thinking "what can I do with these?". Well I had been saving up parts to build one of the tube AM transmitters on phill's site ( I had all but the tubes specified). So I built a transmitter based on the 117L7 circuit on phill's site using the PUNY type 6418 I have in my collection of tubes.

I was able to amplify sound and RF from my signal generator, so I set out to take the osc.(or antenna) transformer and tuning cap I got from a pre-war philco I parted out, and make an RF oscilator.

I got it to oscilate this morning, and tuned it to an empty frequency. I then expermented with different ways to connect the portable cassette player I was using as my audio source in an attempt to get amplitude modulation.

I suceeded! Well sort of...the audio is pretty badly distorted, but I can tune it in on the reciever in the photo if I keep it within a foot or two of of the set up.

It ran well for about 1 hour before the modulation suddenly died. I will need to keep playing with the design to get less audio distortion, but for the time being am over-joyed that it even worked at all.

Here are some photos....


Don't let the disconnected chips fool you....the only active component is the tube in the top right.





If this the wrong section please feel free to move this topic to the right one.