Author Topic: Use of copper tape and capacitance for loop antennas.  (Read 806 times)

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Offline cdev

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Use of copper tape and capacitance for loop antennas.
« on: January 16, 2017, 09:20:30 am »
A way back I had built a pretty nifty loop for shortwave as sort of a proof of concept and now I can't find it. It may have accidentally been tossed out. But let me describe it. It was made from one leaf of a cut to size adjustable window shade. (Soft plastic, the kind that probably isnt so healthy because of all the plasticizers, etc) The plastic was fairly long and I just coated one side of it with aluminum foil and taped the edges. it was soft plastic. When the loop was folded back on itself (and the aluminum not touching the other side, it made a quite good loop antenna which could be adjusted in frequency by adjusting the amount of overlap. You could use it with a shortwave radio in the middle as a weight holding the thing down in the right position.  It is very simple to make. Anyway, I recently bought some copper tape for repairing PCBs and taping shielding and the copper tape would also make a good loop. Smaller tape sizes would likely make good loops for VHF/UHF (with the limitation that the "q" or the capacitor becomes more critical if you intend to transmit. All you do is find a piece of thin, durable, bendable plastic and put the tape on it, then fold the loop back on itself, find the resonant frequency while your pickup loop whatever it is is in its intended position, and then hold it there with some non metal fastening. Tape, especially if its wider than the usual conductors used in loops works quite well. The beauty of this design is that you can also use aluminum foil and it makes not the slightest bit of difference that its aluminum as opposed to copper because there are no solder joints made to it.  So you could literally make a really large, extremely efficient loop out of aluminum foil.

You can tell this is a really hot loop by its extremely sharp tuning peak. When listening with an SDR, when you are off frequency there is literally nothing there but when its on frequency the signals, even weak signals become quite strong. So strong you might even be able to measure them on a voltmeter.  This kind of antenna really allows the very best performance you are ever going to get with the extremely cheap USB dongle rtl2832 SDRs in direct sampling mode.  I am not so excited about their performance on HF with upconverters but with a loop they do quite well for direct sampling. The received signal is cleaner.

Some of my best experiences listening to shortwave have been with a mag loop setup.
« Last Edit: January 16, 2017, 09:25:48 am by cdev »
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