SM0VPO's 80 Meter Spiral Loop Antenna

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Re: SM0VPO's 80 Meter Spiral Loop Antenna

Post by Admin on Tue Sep 11, 2018 4:41 am

Hi again,
Tapping the main loop has been don, but not both tapping and feed loop, to my knowledge.
But there is absolutely no reason why it should not work, from a feed point of view.

The object of the loop is that it's natural resonance (without tuning caps) is just a little above the wanted frequency, for example, about 4 MHz for the 3.5 MHz to 3.8 MHz band. The idea is to have the most wire possible and the smallest tuning capacitor possible. This gives it the best efficiency for this design.

If you want to tap the coil to use other bands, then this will not be possible. You may be able to short turns to get the 4 MHz loop tune 7 MHz, but other bands would be impossible. This has NOT been tried.

If you are using loops and taps for feeding from different sources/impedances then there is no reason whatsoever what it will not work.

BR Harry - SM0VPO

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SM0VPO's 80 Meter Spiral Loop Antenna

Post by Cyrano on Mon Sep 10, 2018 10:36 pm

I want to tap the main coil & also have the feed loop.  Has this been tried?

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Re: SM0VPO's 80 Meter Spiral Loop Antenna

Post by Admin on Mon Sep 10, 2018 8:23 pm

Hi Cyrano,
I presume you mean my http://213.114.131.21/antennas/frameant.htm for 80m?

If I understand you correctly you mean to use a tapping of the main coil instead of adding a feed loop? If this is the case, then yes it will indeed work. It has already been done a few times by other people.

If you do this then perhaps you may want to write a few lines and add a pic? These low size loop antennas seem to be rather popular.

Today I was QRV with a vertical antenna on 3.6MHz, but it is 5.2m tall, ground-plane with a huge coil. I hope to make a comparison between the loop and the base-loaded GP antenna. This could be interesting :-)

BR Harry - SM0VPO

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SM0VPO's 80 Meter Spiral Loop Antenna

Post by Cyrano on Mon Sep 10, 2018 1:32 pm

I'm considering the construction of this 80 meter loop antenna for receive only. My idea would be to tap the other turns of the outer coil with an extension wire from the end of the variable capacitor with a croc/alligator clip. Has anybody tried this? Any comments or input would be appreciated.

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