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Coupling loop question...
开云体育G’day Earl,
I have found that one turn works well.
You can use the spacing to the tuned coil to adjust the coupling.
I think there is a way to estimate a 50Ohm match point but it will depend on the Q of the RC circuit if you can measure that somehow.
Andrew VK5CV.
From: [email protected] <[email protected]> on behalf of Earl Parker II <eparkerii@...>
Sent: Thursday, August 29, 2024 7:56:22 AM To: [email protected] <[email protected]> Subject: [loopantennas] Coupling loop question... ?
I'm building a medium wave antenna, 24" x 24" box loop, 20 AWG wire, 365 pf air gap variable capacitor (at least that's what I'm starting with).? I'd certainly appreciate suggestions on the best design for a coupling loop for such an antenna, thanks!
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Earl
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开云体育One turn it will be then.? As for measuring Q, I'm a long ways from that :).? I'm very slowly learning to speak electronics.Thanks! Earl On 8/28/24 23:23, Andrew Russell wrote:
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开云体育1-T may or may not turn out to be the best solution for your setup. There are usually too many variables to say in general. But in my case 1T did turn out to provide the greatest coupling with a nice frequency response. But my interests are generally VLF.Below is a URL of the tuned loop I made. I was able to quickly evaluate signal strengths and antenna characteristics using 1T, 2T, and 3T.? 2T got crappy and 3T was almost useless. Again YMMV so I suggest you just try different turns. It only takes a few minutes to add a turn and does not have to look pretty for experimental purposes.? GL Gedas, W8BYA EN70JT Light travels faster than sound..... This is why some people appear bright until you hear them speak. On 8/29/2024 12:00 AM, Earl Parker II
wrote:
One turn it will be then.? As for measuring Q, I'm a long ways from that :).? I'm very slowly learning to speak electronics. |
开云体育I shall experiment.? Thanks for the photo.? It looks like it's at least 4 ft square.? How did you arrive at the size and number of turns of wire?? I know there are formulas/calculators; did you use one of those or did other considerations guide you?Earl On 8/29/24 15:43, Gedas wrote:
1-T may or may not turn out to be the best solution for your setup. There are usually too many variables to say in general. But in my case 1T did turn out to provide the greatest coupling with a nice frequency response. But my interests are generally VLF. |
开云体育By all means build your loop then fix it's location & orientation on a known station and establish it's performance with a 1T coupling loop. Then quickly add a 2nd turn and reevaluate, then add a 3rd turn and see which was best.? For my loop I did some hand calculations for the predicted inductance per turn then estimated the number of turns to get me over my target of 3 mH. This allowed my variable capacitor box to achieve resonance from about 25 kHz to about 350 kHz using all the turns in the loop.? If I needed to cover higher frequencies I simply moved my gator clip to a lower number of turns and retuned the cap box. This way I could cover up through the high end of the BC band.? Here was the measured inductance of that loop as a function of number of turns.Gedas, W8BYA EN70JT Light travels faster than sound..... This is why some people appear bright until you hear them speak. On 8/29/2024 4:05 PM, Earl Parker II
wrote:
I shall experiment.? Thanks for the photo.? It looks like it's at least 4 ft square.? How did you arrive at the size and number of turns of wire?? I know there are formulas/calculators; did you use one of those or did other considerations guide you? |
开云体育I started with a 1T coupling loop (haven't tried 2T or 3T yet) and wound up using 9T around my 24" square frame.? I don't have a way to measure inductance but with the old capacitor I have I can tune from 520 to almost 1700, so I figure that's OK for my first effort.? Between tuning and rotating I can get most stations to come in clearly.? This is with everything wire nutted together so I figure that when everything is soldered it might be even better.Earl On 8/29/24 18:35, Gedas wrote:
By all means build your loop then fix it's location & orientation on a known station and establish it's performance with a 1T coupling loop. Then quickly add a 2nd turn and reevaluate, then add a 3rd turn and see which was best.? For my loop I did some hand calculations for the predicted inductance per turn then estimated the number of turns to get me over my target of 3 mH. This allowed my variable capacitor box to achieve resonance from about 25 kHz to about 350 kHz using all the turns in the loop.? If I needed to cover higher frequencies I simply moved my gator clip to a lower number of turns and retuned the cap box. This way I could cover up through the high end of the BC band.? Here was the measured inductance of that loop as a function of number of turns. |
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