Re: lOOP cONSTRUCTION


Chris Moulding
 

Russ,

I'm in the early stages of planning a YouTube video about loop design including the shielded loop and the Mobius loop.  I want to make detailed measurements of signal to noise performance to compare different loops and other antennas in a real situation.

There is an awful lot of incorrect information about shielded loops on the internet including amateur radio text books and the only reference I would recommend with a correct description of how they work is this link by Charles T Rauch Jr, W8JI:

https://www.w8ji.com/magnetic_receiving_loops.htm

For my own use I'm using a split shielded loop 1m diameter made out of coax with the split in the outer shield at the top of the loop. The coax inner conductors come out at the bottom of the loop to feed the Loop Antenna Amplifier. The coax shields at the bottom of the loop are connected by a short wire to clamp onto the BNC shield on the Loop Antenna Amplifier.

If the coax is correctly measured so that the lengths to the split are identical local noise is cancelled out very effectively and subjectively it's the best loop configuration I've used so far. I want to spend some time taking accurate measurements but I need a clear weather window for safe mast work.

The Mobius loop was originally designed as a magnetic probe to measure electromagnetic pulse (EMP) fields during nuclear testing in 1965. It probably works well for that but it's not as good for radio listening as the split screen loop.

If you need a drawing to see what I'm using let me know.

Regards,

Chris

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