Loops Loop on the Ground - deaf?

[dimab]

Bought a LOG kit from LMK. 60 foot wire with transformer.
Setup as square in the yard, connected BNC to my IC705 with a 12” (yes 12 inches) rg316 jumper and heard/saw almost nothing on 20M, 15M, 12M, or 10M.
Even with preamp turned on in the 705 - basically useless. Just barely a few signals.
I compared to my 66’ EFHW and it heard more.
Are my expectations way off base here?
Granted I have crappy solar RFI from the neighbor, and the log was picking that up too.
I could turn the loop 90* to see if directionally it helps, but not expecting for much difference there.
Am I missing anything else in this setup?

Separately I already reached out to ARRL about helping me with solar RFI in the neighborhood. Thank you for the suggestion form another thread.

 

[prcguy]

A loop on the ground is very inefficient and can be down 10dB or more compared to a wire in the sky. It does have its place for stealth and very low noise floor. I don’t have all the key points in front of me but I believe it does best for NVIS but also ok for signals arriving at a low angle Like DX.

The bottom line in HF reception is signal to noise ratio and in my limited experience a LOG produced similar SNR on many bands compared to a tuned wire antenna at 30ft. The signals were a lot stronger on the high wire antenna but the noise floor was an equal amount higher. Unless the LOG is starving the receiver for signal it should work fine and reception should have a pleasantly low noise floor.

 

[dimab]

low noise floor - absolutely. But nothing for DX, which was my main goal. Knowing it’s very lossy, I only ran a 1 foot patch cable to the radio, trying to limit any additional loss. Yet here we are.
My EFHW goes from 13’ to 40ish feet in a tree. Noise floor is pretty bad because of the solar RFI. But certainly gets plenty of DX signals.
Everything I read online - I had much higher hopes. I can’t imagine there is anything wrong with the setup. A wire in a square, terminated at the leads, and a Bnc connection.

 

[prcguy]

low noise floor - absolutely. But nothing for DX, which was my main goal. Knowing it’s very lossy, I only ran a 1 foot patch cable to the radio, trying to limit any additional loss. Yet here we are.
My EFHW goes from 13’ to 40ish feet in a tree. Noise floor is pretty bad because of the solar RFI. But certainly gets plenty of DX signals.
Everything I read online - I had much higher hopes. I can’t imagine there is anything wrong with the setup. A wire in a square, terminated at the leads, and a Bnc connection.

What is the LOG sitting on?

 

[13dka]

Since you already ran the radio directly down at the antenna (I think) with the patch cable, RFI creeping down the feedline to the antenna is obviously not the issue. (Another often overlooked issue with lossy antennas is how important shielding becomes when the little signal they deliver is running through nn feet of cable, through the noise halo of your house and whatnot.)

Chances are that your neighbor's solar inverter (how bad is it? Any frequency ranges not affected?) isn't the only source of near-field RFI, and LOGs are not any better than other loops in mitigating that. Unfortunately, some of those sources are not easy to identify because it's basically just wideband noise that sounds like regular static. However, rotating the LOG is something you could try. Another thing to consider in this context is that LOGs are bidirectional only for flat elevation angles, for high incidence signals (e.g. from a roof) they're increasingly omnidirectional. Related to that, your ground may have some influence on your happiness with it - if you have low ground conductivity the LOG could have a pretty steep takeoff angle, which isn't ideal for DX. On very good (moist) ground the (ground-) losses increase massively but it behaves just like any other vertical polarized antenna - the takeoff angle is decreasing.


Left: Poor ground, elevation angle ~40°. Right: Good ground, elevation angle 15°

The 705 (on P.AMP 2) does have the gain reserve to deal OK with a passive LOG, but the output isn't exactly knocking your socks off, particularly on the higher bands. I had good results with a passive LOG anyway, but that was in a zero noise environment. The SNR advantage can be considerable though compared to unsymmetrical endfeds, verticals etc, when a little local noise is present.

 

[dimab]

What is the LOG sitting on?

Grass. Directly on the ground.

 

[ka3jjz]

A little homework in our Loops wiki would bring a lot of information to the front, I'm pretty sure at least some of this mentioned the use of a preamp to overcome the lossy performance....and there's even a FB group devoted to the subject

Loops - The RadioReference Wiki

wiki.radioreference.com

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and I would imagine there's more to be had using your Google-fu (heh)

Mike

 

[13dka]

I'm afraid increasing sensitivity won't really help here, since an LNA would not really increase SNR when there's RFI. Without the RFI it sure brings more joy to the LOG, because very faint signals can otherwise drop below the receiver noise. With a 60' circumference loop the LNA needs to have a pretty good IP though, a simple LANA HF etc. will just overload and a nearby AM station may make a band stop filter necessary... a lot of hassle, worthwhile only without local QRM.

Maybe more information on how the LOG is located between the houses could give us some ideas. Here's a rough idea what the ground conductivity is like in dimab's neck of the woods:

 

[ka3jjz]

You could solve some of that by using one of W6LVP's experimenter kits. Larry has been known to add filters in the preamp (where they really should be in the first place) for BC interference - something none of the other loop manufacturers will..

W6LVP Magnetic Loop Antenna Experimenter’s Kit | W6LVP

www.w6lvp.com

An email to him won't cost anything....Mike