A potato by any other name

Researching foxhole radios and early radio wave detectors uncovers a lot of clever and strange equipment improvised by early radio amateurs. Like this radio wave detector made from a potato from the July 1915 issue of The Electrical Experimenter, invented by Milton Rochkind. As he explains it:

While putting up an aerial in my yard (80 feet long and 60 feet high) recently I tried to receive wireless messages. I took a potato and placed it on a box. Then I took two sewing needles. I took one needle and stuck it into one side of the potato. I then connected the second needle with one pole of the receiver and stuck it in the other end of the potato. I took the ground wire and connected it with the other end of the pole of the receiver, and when this was completed I was able to receive many messages just as clearly as from a detector.

The editor assumed the potato was acting like an electrolytic detector, a common detector of the era. I tried repeating the experiment but never got a signal. If anyone reading this manages to make a working radio from a potato I would love to hear about it. 

There were an amazing variety of radio wave detectors in the pre-crystal and vacuum tube days. They are well covered in Vivian J. Phillips' Early Radio Wave Detectors. Stevenage, Hertfordshire, England: P. Peregrinus in association with the Science Museum, London, 1980.

I'm ready for my close-up

 If you've ever wondered what a razor blade looks like magnified 500 times, this is it. I was having it analyzed to see if there was any surface chemistry that would make it a good detector for radio waves. This is a WWII era "blue" blade. Despite popular folklore to the contrary, there was no selenium present. SEM image by Houston Electron Microscopy, Inc.

Here's the same blade at 75x.

The iron oxide is likely magnetite, which can act as a semiconductor. It is a thin enough layer that it allows some light to pass through, causing thin-film interference, similar to the surface of a soap bubble. This accounts for the subtle blue color of the blade.