HFU HF Underground

Technical Topics => Equipment => Topic started by: Antennae on September 12, 2016, 1628 UTC

Title: LoG receive antenna, Loop on Ground!
Post by: Antennae on September 12, 2016, 1628 UTC
Its a loop flush on the ground. You can also phase the things for directionality!  Cool shtuff, mang.  Check out the website with pictures:
http://www.kk5jy.net/LoG/
Title: Re: LoG receive antenna, Loop on Ground!
Post by: Pigmeat on September 13, 2016, 0846 UTC
I like them. We had a particularly noisy summer about 14-15 years ago when no one was getting out well, not even KIPM which was running a buttload of power. I started screwing around with things after reading an article in ham mag about them. I was using around 145 ft. of wire, close to a full wavelength for the funny band. That thing was near dead quiet. I used a small MFJ tuner for it. I could peak the signal on the loop, then adjust the gain on the portable, a DX-398 like you have, to hit that sweet spot where the signal could be best copied. They're not really for gain, they quiet the noise down enough to allow what's out there to be heard.

If you wanted to boost the gain, you could unfasten the end of the loop going to the ground terminal of the tuner. It was still a very quiet antenna, but not a closed loop. It's something you have to experiment with. Sometimes the complete loop can be so lossy as to be near dead. I found that to be the case when using the big radios in the dead of winter with it, when I was sure it was going to kick butt. Different ground capacity and atmospheric conditions would be my guess. I'd unhook the ground side and the band would come alive, but it still wouldn't outperform a dipole cut to frequency and well elevated in the quiet season. Or a BOG for that matter.

Have fun with it. The ground doesn't freeze hard as rock out your way like it does where I live. It might prove to be a good all year antenna for you.
Title: Re: LoG receive antenna, Loop on Ground!
Post by: Josh on September 23, 2016, 1619 UTC
Some of the arrl antenna compendiums have on ground and in ground hf antenna articles. They make for interesting reading.
Title: Re: LoG receive antenna, Loop on Ground!
Post by: RobRich on October 24, 2016, 0020 UTC
I have an 148' square loop on the ground. It is a "shielded" coaxial loop design. Why shielded? I have lots of RG-6 coax available, so I figured why not? Likely does not matter much, if at all, but anyway.

Interestingly enough, it is my primary LW, MW, and HF receiving antenna. I sometimes use a preamp, though it is rarely needed for frequencies under 15MHz.

I have attached my extraordinarily basic - as in Paint.NET ;) - antenna details below. I went for a loop size slightly larger than a wavelength at the 40M band, but being on the ground, the actual resonance could be (and probably is) much lower.

There used to be a dedicated balun at the feedpoint, but it offered little to no discernible difference, so it was replaced with a direct coaxial feed as depicted and several snap-on ferrites on the feedline. I do use a common mode choke (~3000-ohms rating at HF) back near the attached receiver, though it is not really needed either IMO.