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Any info about making air variable capacitors, and magnetic loops?

Simon Thompson #28668 开云体育 I think they are ok for receive; the deep null they can produce is beneficial in some circumstances. I think that if you used two loops on receive, it would be a highly directional array; in fact, I believe I have seen similar setups on aircraft for RDF. toggle quoted message Show quoted text On Jun 21, 2017, at 1:33 PM, John Smith via Groups.Io <johnlinux77@...> wrote: I think that was well said all the way around. What do you think of them as receive only antennas, both as a two antenna system, and just for receivers only? If anyone is wondering what I mean by two antenna system, think about the Beverage antenna as receive only, and something else for transmit. This comes to mind because of the loops directivity and high Q, aka, less noise and QRM reception. So, is it equally inefficient at reception?? On Wed, Jun 21, 2017 at 12:24 pm, Simon Thompson wrote: The size of loop required above 20 m for any kind of transmission efficiency makes their use highly inefficient. I think they are neat antennas, and interesting in many ways, and I have made and used them myself, but I think of them, literally, as a last resort. Almost anything is better than a mag-loop; I know some people have success making qsos with them, but operators also make qsos with dummy loads. Even a short wire and counterpoise attached to some coax and a balun will work much better than a tuned loop. I know there will be people who reflexively respond to this with their own tales of amazing results, but a larger, more efficient antenna will almost always outperform a smaller, less efficient antenna.
John Smith All Messages By This Member #28669 Hey Rich, I printed the drafted image at the bottom of this site. As printed the width of the rotor is 2 3/4". It seems like a workable size for cutting a stack of sheet metal sandwiched between two layers of thin plywood taped together on a scroll saw. I can make more rotors and stators?for more capacitance. http://fucimin.altervista.org/en/loop.html Any comments about the size, and construction tips? toggle quoted message Show quoted text On Wed, Jun 21, 2017 at 12:26 pm, Richard Andrew Knack wrote: If anybody is interested I have a file somewhere that gives dimensions for a "butterfly" capacitor... ?
John Smith All Messages By This Member #28677 Thank you everyone. I got a lot of new info from here and google. Nobody around here has any experience with the mag loop, but there are two of us, myself and an extra class operator who are planning a build for the experience. And he is the person who recommended the BITX40 to me in the first place. But he hasn't assembled either of his two analog and digital BITXes. So, I am not to concerned about him constructing one first. Hi Hi. Even a little friendly competition can help improve one's amateur radio skills. Thanks again.
Vince Vielhaber #28690 If you're on Facebook, there are two groups dedicated to magnetic loop antennas. Vince. toggle quoted message Show quoted text Thank you everyone. I got a lot of new info from here and google. Nobody around here has any experience with the mag loop, but there are two of us, myself and an extra class operator who are planning a build for the experience. And he is the person who recommended the BITX40 to me in the first place. But he hasn't assembled either of his two analog and digital BITXes. So, I am not to concerned about him constructing one first. Hi Hi. Even a little friendly competition can help improve one's amateur radio skills. Thanks again. -- Michigan VHF Corp.

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