Re: Why not a resonant loop?
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Great, but it's narrow banded!? Again, my interests in loops range from below the submarine comms. (Schumann Resonance) through 160-meters.??
I have a tuned loop for 40, 30, and 20-meters, but here at 5800-feet elevation, even a 2.5 kV variable capacitor for resonating the loop arcs with even 50-watts.? Using a standard 365 pF BC variable is totally out of the question.? I finally had to buy a vacuum capacitor rated for 15 kV to operate at 100-watts comfortably.? Yes, it's an overkill.? And again, the 2 : 1 bandwidth on that 1-meter diameter tuned loop is 3 to 5 kHz wide.? To resonate my 2-meter "shielded" loop made of 2-inch OD copper pipe (hexagonal) out on the eastern hogback at the Schumann Resonance presents quite a challenge and each harmonic of the nominal 7 Hz fundamental would just further complicate the logistics. ? This also applies to all the submarine comm. frequencies.? No thanks to resonated loops for my applications.
EXAMPLE:? Assume 10-?H inductance for that 2-meter "shielded" loop the nominal Schuman Resonance frequency of 7 Hz.
10 ?H at 7 Hz = + j 440 ?Ohms ? ? ?? Yes, that's MICRO-ohms!!
To resonate with a capacitor, that would require a capacitor of? 51.7 FARADS.? That's FARADS, NOT MILLIFarads and NOT MICROFarads!? Yea......sure......I don't think so.......?
And take a submarine comm. frequency of nominally 20 kHz:
10 ?H at 20 kHz = 1.26 Ohms
To resonate with a capacitor, that would require a capacitor of 6.32 ?F.? Well, at least that' within reason. ?
Dave - W?LEV
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Reply to Mikek:
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I use an 11 turn flat (pancake) wound loop to chase broadcast-band Dx in the US.? The loop tunes from about 700 hHz to a little over 1600 kHz. A small silver mica cap can be switched in to tune down to 500 kHz.? A single turn coupling loop diameter about 5” feeds the receiver through shielded twisted pair.?
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