Oral History of Defence Electronics

R G Wells: Creating the capcitor. The problem building the set, of course, was the need to build components, so until we could build some components there was nothing much we could do. A look at the circuit diagram of a regenerative receiver indicates a number of capacitors - about two or three are required - low capacitors to make the oscillating part of the system work, and in fact from memory we needed in the grid circuit at least one .01 microfarad capacitor and there was no chance we could get this anywhere, or any other components. So we hit upon the idea of taking some tin foil or aluminium foil from the tea chest which the Japanese supplied with the rice rations, then by the well known equations for calculating capacity and the relationship of the distance between the plates and the area of the plates we built a capacitor or, at least, I built a capacitor which according to calculations should have been about .01 microfarad. If I could put an aside here, I built a replica of this capacitor some years ago, and it went out to Simpson barracks where we had some friends in the testing laboratory, and with great excitement the Warrant Officer concerned said "We will see how good your calculations were"; so he pwt it on his equipment which was accurate to many decimal points and read on his display unit .009 microfarad, so we thought we were pretty good. I said "Touché" to him because he didn't think we could do it. I made two or three of these, and I still have one of them that would work if I built the receiver again, which I have been thinking about doing but there's always something else, like a lot of other projects which one has as one gets older. We had to insulate the layers of [the capacitators] which we did by putting a layer of newspaper (a few people had newspaper and various things, for other reasons than newspaper of course, but then we had no other toilet requisites in the party) and by soaking this in some coconut oil we could insulate each layer after we wound it, and with a piece of this bee wire - we had something like fifty feet of it - wound round this part of the fish plate, we made a fairly good choke coil. And then a bigger capacitor, which was no trouble, having had success with the small one, to just wrap as much tin foil as we could round another sheet of newspaper which finished up about 18 inches long by about three quarters of an inch in diameter. We didn't even try to measure the capacitance of it, because we couldn't do anything about it anyway, except put more wire on. And that in effect was a fairly good rectifier, a very dangerous one because we had the 110 all right but we had a bit over that by the time we had rectified it, and we don't know because we had no means of measuring it.

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