Monday, August 12, 2019

Roll up coaxial cable magnetic loop

Efficient magnetic loops can be made fairly small but due to their rigidity can still be heavy and bulky to carry in packed luggage. If high performance and power handling capability are not required one work-around is to make the loop from coaxial cable braid. This approach is used in the popular Alexloop used by pedestrian mobile operators. I've worked a couple of stations on 40 metres using such antennas and as expected signals have been weak.

Results can be improved if you use a longer conductor length. Here I use about 7 metres of coaxial cable connected to a variable capacitor. A toroid is threaded over the cable with a few turns of wire providing coupling from the transceiver. Below is a description and demonstration of an experimental loop set up in an open area.



Inspiration for my loop came from G4FON's website. The above loop is nearest to the version 2 described.

PS: Into low power amateur radio? Minimum QRP is the top-selling manual on the equipment, antennas, operating and strategy of successful QRP operating. It's available for under $US 5 each in electronic form. Or you can get a paperback version. Visit VK3YE Radio Books to find out more. 



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