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.
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