You might look at Peter Yanczer's book online
https://www.earlytelevision.org/pdf/...television.pdf
Chapter nine discusses building a camera and receiver. It's a different camera and receiver then his kit but Peter probably used the ideas from his kit to build this other camera and receiver. There are schematics for a video amp in Chapter 7.
I have my mechanical tv camera here at home and my mechanical tv receiver in Storage about 7 miles away. You should be able to record the output of the camera as an audio signal to computer sound card, audio tape or CD/DVD etc. I think the CD from the narrow band television association that Wayne mentioned is recorded images from a camera in their format. I would suggest experimenting with a stationary image at first. I think Peter provided a large bold letter "A" printed on a 8 1/2 x 11 piece of paper for this purpose. I will try getting out to my storage area and bringing my receiver home. I'll hook my camera-receiver up and see if it still works. If it does I could record an audio file of the image and send it to you as a .wav or mp3 file. This would help isolate if it's your camera or receiver causing the problem.
-Richard