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LOG (Loop On Ground) Antenna




 
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Author Topic: LOG (Loop On Ground) Antenna  (Read 1861 times)
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WA2SQQ
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« on: August 16, 2018, 01:50:24 PM »

I'm wondering if anyone has ever used one of these receiving antenna's? "Loop on Ground" is a 60ft loop of wire, configured as a square, and fed with the appropriate balun. It sits on the ground and is said to be a very low nise receiving antenna. Of more interest is its bidirectional characteristic. Looks like it could be an interesting 160m antenna for this winter.

http://www.kk5jy.net/LoG/
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W1ITT
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« Reply #1 on: August 16, 2018, 02:15:12 PM »

The LOG antenna looks like another good piece in the lowband toolkit.  Note, however, that modeling shows that the signal produced by the antenna is minus 30 db or so.  This indicates that attention needs to be paid to minimizing common mode currents on the line coupling into the antenna and subsequently fed to the receiver.  Common mode signals can easily compete with these minus 30 db levels.  The simple binocular balun transformer may well need some help.  On any of these low-output antennas, I use a ferrite toroid and wind as many turns of coaxial cable through it as I can, placed next to the balun.  We want to be listening to the antenna, and not to all the buzzies that get coupled to the coax run back to the shack.
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KD6VXI
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« Reply #2 on: August 16, 2018, 02:35:20 PM »

K7FP metalwerks has some largish ferrite in stock last time I checked for making decent common mode chokes.

It's amazing how much your receive noise level and RFI on TX can be minimized by a ten dollar ferrite!

--Shane
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W1ITT
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« Reply #3 on: August 16, 2018, 04:19:26 PM »

Shane..

Yup, I buy my ferrites from K7FP.  He has good prices, stocks what you need and gets it on the wagon pronto.  I'm doing a high isolation balun design project now and have a whole passel of them in front of me.
Norm
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WA2SQQ
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« Reply #4 on: August 16, 2018, 08:37:33 PM »

Thanks for the K7FP TIP
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KD6VXI
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« Reply #5 on: August 16, 2018, 10:35:29 PM »

Not a problem.  He's a good guy, and he has some stuff you generally don't find at hamcentric stores.

I get all my stuff from him, even cores to build filament chokes.

--Shane
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Patrick J. / KD5OEI
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« Reply #6 on: August 19, 2018, 12:46:31 AM »

Dennis Brady W5FRS uses one and swears by it eliminating all kinds of noise.
I tried one 40x40 rectangle and didn't get good results. Probably did it wrong.
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Radio Candelstein - Flagship Station of the NRK Radio Network.
WD8BIL
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« Reply #7 on: August 19, 2018, 08:29:59 AM »

Common mode noise in these antennas is largely induced in the feedline. Many articles are available to combat this.

One sure method of overcoming this is with a good LNA right at the feed point. Pump the intended signal up as high as you can get it.

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K6IC
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« Reply #8 on: August 21, 2018, 12:19:35 PM »

Will add,   that KF7P Metalworks also sells Ferrites,   and many,  many other things.   The metal products that he builds are also top-notch:

http://kf7p.com/KF7P/Ferrite_chokes.html

His mast steps are most excellent ...   and so on.

GL,   Vic
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K0OKS
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« Reply #9 on: January 04, 2019, 12:57:43 PM »

I have been using a LOG antenna for a few months now. It is very good for reducing atmospheric noise, especially lightning crashes. However, it does have significant attenuation. So it works best for ragchewing with stronger signals.

I connect mine to the sense antenna port of an MFJ 1026 noise cancelled/signal enhancer and use that to “mix” the main antenna with the Loop on the ground antenna. I start with just the Loop and then mix in enough of the main antenna to copy the signal clearly. With strong signals it could be all the LOG. Weaker ones require more of the main antenna. The ability to mix the two is significant, and the results are much nicer than just the main wire antenna.

I do not yet have a LNA in the Loop, but do plan on adding one. I am using LMR-400 to connect it, though.

Of course you need to ground the receive antenna when transmitting to avoid overloads.
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PA0NVD
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« Reply #10 on: January 04, 2019, 01:42:11 PM »

A good way to reduce line pick-up is using a transformer, not a choke. A transformer at a ring core with two opposite coils can easily compete or out perform a choke wrt the line pick-up. And a few dB more attenuation isn't noticed when the antenna is already 30 dB down.
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Steve - K4HX
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« Reply #11 on: January 06, 2019, 10:44:32 AM »

A transformer balun may be better a very low frequencies (AM BC and below), otherwise, they are no better. Galvanic isolation is not signal isolation.

Another good way to reduce feedline pick up is to bury your feedline. I've done that with all my loops and Beverages.
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