Annotate Crystal TV

This idea is inspired by a comment by [nineteenthly] on another idea, which I'll link below.

I'm using the exact same principles as the crystal radio, but this is going to output an image.

Quick summary of a "crystal set" radio: Antenna, coil, diode, earphone, ground. Attach antenna to a tap on the side of the coil, the diode to the end, earphone to the diode and to the other end of the coil, and from that point connect the ground. The coil/antenna pair selects the radio signal; the diode retrieves the audio signal that was Amplitude Modulated onto it. (AM radio, see?)

OK, now we make a change. We're going to take the diode out of the circuit, and replace it with an LED. It gets glued to the side of a finely threaded rod. Then a very fine tube (about the size of a 10ga hypodermic needle) is attached (epoxy might be good) to the LED in such a way that the emitted light can be seen down the tube. The LED should then be covered so no light escapes any other way.

Now take a nut which will fit on the threaded rod. Braze a frame onto it such that you can have a piece of PVC pipe sticking out one way, and a crank handle sticking out the other.

Next, a toothpick will go into the inside of the pipe. Lengthwise, and positioned so that the light tube points at it when you've got the crank handle in the farthest position from your body. The light tube has to be just short enough to not hit the toothpick when the crank is turned. (I would have said that earlier, but you would have said "What toothpick?")

Finally, you'll need to put a piece of photosensitive paper or film into the PVC pipe. This should be cut so that it is slightly shorter than the inner circumference of the pipe. (Did I mention that this will be done in a darkroom? At least the cutting & using, anyway.) When it's the right length, the edges of the paper or film will slip under the edges of the toothpick and be held in place.

Now, you get your local radio station to transmit a picture. (Exercise for the reader, obviously.) The picture will be transmitted as sound levels, lowest for bright areas, loudest for dark; preferable to have them transmit borders on the left and right. Each scan across the picture will then be very rhythmic, with a definite break in between scans.

So you will be standing in your darkroom, listening to the earphone as the content of the picture is described; you make the decision that you want to "download" this image. You grab the crank, and start turning it as you are given a 5-count to get your timing steady, and then crank-crank-crank to the rhythm of the pshshshst - pshshshst - pshshshst of the image bands.

Then, a dip in the Dektol, the stop bath, the fixer, the wash, and viola!

(or was that a lute? the neck is kind of bent, or did you not turn the crank evenly?...)