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Old December 7th 14, 03:01 AM posted to rec.radio.shortwave
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Default Continued success with small magnetically-coupled loop

Hi folks,

So a couple weeks in, and I am consistently getting vastly superior results with my indoor passive loop vs. the internal whip. Did some measurements of indicated S/N ratio on Tecsun PL-360 (it's actually carrier to noise ratio.) Yes, you can plug an SW antenna into the "AM" jack and it does work.

The improvement is usually at least 10 dB and sometimes better than 20 dB according to the indicated S+N/N readings. This is confirmed by switching back to whip and noting that most signals less than 10-15 dB are completely lost on the whip and are copyable on the loop.

It's not about signal level because adding the wire from Tecsun PL-660 in the same room, it increases the signal but makes little difference on copyability.



If you're looking for a decent indoor antenna that requires no batteries and can be used in a portable context, the 9:1 balun (not un-un) magnetically coupled small loop is definitely worth a serious look.

One mini-circuits T9-1 transformer, high impedance side connected to 10-25 feet of wire on both ends. Use alligator clips or a box to attach leads to transformer. Solder twisty pairs to secondary and to an 1/8" plug to radio. Keep the radio portion as short as possible. Hang the wire in a delta loop configuration using two available supports. Try to maximize the area of your loop. Results are a dramatic drop in background noise pickup below 10 Mhz.

For what it's worth, feel free to give it a try. It really seems to make an improvement.

-- ross



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