Having detected the Sun at 70cm with a 15m length of Aircell 5 cable I realised that it was definitely too long; the loss was probably about 3dB. So I wondered what the losses would be for various other bits of cable I had lying around, especially with the connectors on. So here’s the test setup; simply using the FT-817 at its 4 power settings to put a 70cm signal through a cable and meansure the power (roughly!) compared to the power without a cable. The power is absorbed in a little dummy load made from a small 50 ohm power resistor (designed for such a purpose, and extracted from an old bit of microwave kit) on a heat sink.

I have a device which is a forward and reflected power meter, uncalibrated, except that I have a good idea of the relative levels for its various range settings. I call it the “Sparrow“!

The measurements turned out to be fairly interesting but not unexpected; I calculated losses for various lengths of Aircell 5, URM67, RG58 (!) and 4 metres of Heliax of some sort. The losses measured were similar to what I would have expected from published figures for the cables, which is reassuring.

I also made a set of measurements with on cable both with and without a fine assembly of connectors, to see what extra loss was involved. Not a lot (compared to the differences between cables, but easily measurable!