Looks like teflon has a sufficiently low loss tangent, is being used successfully as a dielectric on mag loops.
I'm sure a vacuum for the dielectric is preferred, but nothing costs way too much.
Could be compression, book, or trombone style, but having the cap be one piece with the copper loop
should be a win, assuming it can somehow be mechanically stable enough to stay tuned within a few khz.
Yes, it would be tough to get this to work well, currents are tens of amps, several kV across the cap.
But I don't yet see what is inherently wrong or inefficient with overlapping two strips of copper with a teflon dielectric.
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No soldering between loop and cap?
That rules out most of the mag loop construction techniques I've seen.
And an argument to try overlapping the two ends of a copper strip to form a cap.
Jerry, KE7ER
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On Sat, Dec 21, 2019 at 01:29 PM, Kirk Kleinschmidt wrote:
Those are all great ideas...until you try them. :)
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Mag loops don't work (well) unless we build them in ways that only mag loops require. Overlapping strip capacitors, as you describe, while they will "work" after a fashion, have huge losses in mag loop applications, and they don't stay stable with temperature and humidity, etc.
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Loop conductors should be continuous and NEVER soldered. Capacitors should be vacuum variable or butterfly types with no mechanical wipers/contacts (huge losses). Mag loops in no way work like the antennas we're all used to, and different (weird?) construction techniques are required to make a good one.
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Read this from Leigh, a VK5 expert in mag loop design and the underlying science. See:
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There a lots of junky mag loops on Youtube, etc. They work -- as do 6-inch whip antennas -- just not very well.
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There are some mag loop groups here on .io
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Properly built mag loops are awesome. The opposite is also true :)
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Good luck,
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--Kirk, NT0Z
? Rochester, MN
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My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)
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