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Author Topic: Loop on Ground - initial results  (Read 460 times)

Offline ChrisSmolinski

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Loop on Ground - initial results
« on: November 06, 2018, 1918 UTC »
Reference this article for the general idea(s) behind the LoG antenna: http://www.kk5jy.net/LoG/?fbclid=IwAR0dDk21M6XqZg7IwQ5NE7ggmS5Ux6Ivc_-_gtSZpE9Qbeu4EB9h5T4NGyU

My first attempt at the LoG antenna was using 500 ft of wire, I wanted something that would work well on MW and perhaps even LW, and was curious how it would perform on HF. The weather has not been cooperating, with nearly continuous rain. This means I've only had a few brief windows to do work, and not really spend as much time as I would prefer optimizing things. Yesterday afternoon I got the wire run, not in a square or rectangle unfortunately, but as I am not looking for a particular pattern, I wasn't too concerned.  The weather plus early darkness now that we're close to winter didn't allow me to optimally match the antenna to the RG-6 coax feedline, so I went with a roughly 3:1 (might have been higher) ratio on one of my Squid universal matching transformers.  Performance was.... eh. Lots of buzzing which sounded like 60 Hz harmonics on the lower end of MW. Not great performance on HF, but it's several wavelengths long, so that's probably as expected.

This morning there was a break in the rain, so I played around with the matching. Turns out the best ratio from a S/N perspective was 3:2, at least on MW.  I then went back in the shack and checked out the MW band. My comparison antenna was my 670 ft sky loop antenna. In some ways this LoG is very similar, it's almost the same size, just laying on the ground. On MW, results are mixed, there's some cases where the LoG definately wins, others where the sky loop wins. Sometimes they picked up different stations, so there's obviously (perhaps significantly) different patterns. Which isn't a bad thing, if you don't like the DX on one antenna, switch to another.  On the upper end of MW the sky loop was the overall winner, but that's where it is about a wavelength long.  HF performance was not that great. OK, it was pretty dismal. But again, this was a 500 ft long LoG.

With a break in the rain I decided to reduce the size down to 25 by 25 ft, and see how it did on HF. I ended up using a slightly higher turns ratio on the Squid transformer, 2:1 I believe.  MW performance of course got considerably worse as expected. I'm not sure that HF performance improved that much, comparing against some daytime targets like CHU 3330/7850, CFRX 6070, Cuba on 5025, and whatever SWBC stations from Europe were coming in fainting on 49m, as well as stations on 31m, In every case, without exception, the sky loop was the winner, usually by a large margin.  For 49m, my 43m dipole was also the winner, vs the LoG.

I then decided to switch back to the original 500 ft design, as there's some advantages vs the sky loop on MW. And with some more antenna wire, I can make it larger, perhaps around 800 ft, as well as closer to a rectangle in layout. I'll be interested in seeing how it performs once modified.

I live in a fairly low noise rural area. It's entirely possible that for suburban or urban DXers the LoG has some significant advantages vs dipoles or random wire antennas. And if you absolutely cannot get an antenna in the air due to HOA or other restrictions, it certainly seems like a viable alternative to in-the-air antennas.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
NRD 545 / netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop