Technical Topics > Equipment

Can a LoG be too big?

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NJQA:

--- Quote from: ChrisSmolinski on November 28, 2022, 1752 UTC ---   The only way to make one last (here anyway) would be to use large gauge wire, which is cost prohibitive.

--- End quote ---

I’m going to try another loop this year….a bit smaller, maybe 500 ft.  This time I will use #14 THHN electrical wire (I used cheap CCA CAT5 last time).  I’m hopping this will be more rodent resistant.  I’ve got no idea how sunlight tolerant THHN is, but I will know soon enough.

THHN has jumped in price - a few years ago a 500 ft spool was about $50.  Today it is closer to $80.

NJQA:

--- Quote from: RobRich on November 29, 2022, 0035 UTC ---Do not put too much thought into impedance transformation IMO. An 1:1 should suffice if needing additional isolation for common mode, though admittedly I ran my LoG for many years without any balun or transformer. 1:1, 4:1, or whatever else tried when constructed did not affect it much. FWIW, there were just a few relatively useless ferrites on the feedline near the feedpoint.

--- End quote ---

I think that a significant part of a successful LoG is suppressing common mode pickup on the feedline.  I would either use ferrite cores (type 77 or 75 if your interest is LF) or a CM filter (KD9SV and DXEngineering sell them).  Place a filter at the antenna feedpoint and at the receiver.  Burying the feedline helps a lot and may even negate the need for the common mode filter.

RobRich:
I use KD9SV common mode chokes on some feedlines. I never bothered measuring them, but I suspect it might be a mix 7x ferrite considering much of his product line is biased towards the 160m and 80m amatuer bands.

If just receiving at HF and lower frequencies, even a small mix 73 binocular core with a 4:4 or whatever isolation winding often will suffice for basic common mode choking. The popular BN-73-202 is about $1 each or sometimes less in small quantities. For that price place one on each end of the coaxial feedline. For those not wanting to solder, even a terminal block will suffice for HF and below.

Another aspect to consider is differential noise mitigation, which can be helped by balancing the loop currents through good symmetry and/or design considerations. Many of the "shielded" magnetic loop designs are more about balancing loop currents than actual effective electrostatic "shielding."

I plan to soon replace my old LoG, and I will likely again use a "shielded" coaxial design. I have an 1000' spool of decent Belden RG-11 for feedline on the way, but I am leaning towards again using cheap RG-6 for the actual loop antenna. I probably have plenty of RG-6 on partial spools here to build the loop, but for those buying, an 1000' spool of flooded direct bury bulk RG-6 is under $100 shipped on eBay. That builds several typical LoGs or one quite large LoG.

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I am a huge fan and user of LoG antennas, but being realistic about LW to MW reception, a remotely-tuned FSL antenna on a rotator is likely the "better" solution for serious DX'ing of low frequencies.

NJQA:

--- Quote from: RobRich on November 29, 2022, 2309 UTC ---….but for those buying, an 1000' spool of flooded direct bury bulk RG-6 is under $100 shipped on eBay. That builds several typical LoGs or one quite large LoG.

--- End quote ---

Good point, but I will stick with the THHN wire for this season because I still think the squirrels will still be a
problem.  Repairing a wire break will be much easier.

Pigmeat:
Squirrels are rodents, rodents gnaw on anything that will sharpen their teeth including you, (try to pet one). You can shoot them, you can poison them(use rat poison, they're nothing but tree rats, info the rat poison folks are loathe to put it on the box.),you can bop them with a projectile from your antenna line slingshot,there are lot's of way's to get rid of them. Just kill the things. I suspect old fashioned mole traps would do the trick for ground squirrels. A couple of bloodthirsty 10 year olds w/ .410 shotguns should keep all of them in check nicely.

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