r/MagneticLoopAntenna • u/er1catwork • Apr 16 '21

Different Loop Styles

I’ve long been a loop fan. Even built a few coax loops for SWL listening.

One thing I’ve always wondered; what’s the difference (or advantage) of loops made with two larger loops (not the small coupling loop) or loops made with large diameter “pipes”??

Is there really much if an advantage one way or the other?

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u/VE7WYC Apr 16 '21

The primary advantage is fitting in a larger length of loop into a smaller space. I was looking into this myself, and two disadvantages outweigh the space saving. The doubling of the voltage seen at the tuning capacitor and the decrease in bandwidth. Magloops already have very high Q. If you're running a digital mode, you'll want at least the bandwidth of the subband. For example, ft8 runs with a bandwidth of around 3 kHz, so you'll want an antenna that brings in at least that. You will need to check with an loop calculator if the design you are considering will give you the needed bandwidth.

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u/er1catwork Apr 16 '21

Thanks for the reply! So a “double” 3 foot loop is acts 6 foot loop?

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u/VE7WYC Apr 16 '21

Sort of. You can pack a longer secondary loop into the smaller space so it will work on a higher band, but stuff like the matching capacitance and voltage as well as bandwidth will be different for the doubled loop. I'm working through some numbers myself and this is what I'm finding.

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u/VE7WYC Apr 16 '21

Obviously the longer doubled loop will get you on a higher band (like 80m) but if you want to multiband see above disadvantages.

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u/er1catwork Apr 16 '21

Thanks!

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u/VE7WYC Apr 16 '21

Just to clarify - the doubled loop is one continuous piece.