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Saturday, July 04, 2009

How to build a radio in a POW camp

By Cory Doctorow in Boing Boing:
This first-hand account of the construction of a clandestine shortwave radio by British POWs in a Japanese camp in Singapore really reminds me of James Clavell's magnificent novel King Rat, my all-time favorite war-novel, which revolves grippingly around the construction, discovery and consequences of a hidden shortwave in the Changi camp (both Clavell and Ronald "St Trinian's" Searle were interned in this camp).

BJ: Can I just ask you - the components for the low voltage battery cells that you produced, where did you get all the components from?

RGW: Well, zinc wasn't hard, there was some sheet zinc lying on the aerodrome and we pinched quite a bit of that because that would be eaten away during the use of the cells for the low voltage. I don't know what would have happened if that ran out. I think someone produced two lantern cells which did for a while, but it was mainly on this home-made cell system, which wasn't efficient but nowhere near as inefficient as the rectifier was. We must have been consuming... Ah Ping said he had to turn up a lot of power to keep the lights what they wanted. We were dispersing such an amount of power in this four test tube rectifier for the high tension.

A variable capacitor was another component we had to bring in. We couldn't make a variable capacitor, it was impossible. We had to take two plates off the one we had to get a high enough frequency. Yes, I can't remember why we didn't go up a bit in inductance; it was largely a trial and error business really. Except that in a regenerative receiver you had some idea when you were near a station because the receiver was so sensitive as all regenerative receivers are.

It had a piece of meat skewer type wood which I had a hole drilled in by a pen-knife, and we glued this in with some of our glue or something, into the capacitor shaft so that we could tune it by holding a little stick across it, fixing it at about six inches because one couldn't get one's hands any closer to the set because it was in a state of very near oscillation where the maximum sensitivity is, just before it bursts into oscillation. With a fairly clear HF band, it wasn't long before we knew roughly, by putting a couple of marks on the stick, where it was. We knew that the Voice of America was due for a transmission and I don't think we ever knew the frequencies because the BBC didn't announce frequencies, they just came on the air and broadcast.


Construction of Radio Equipment in a Japanese POW Camp (via Make).

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