Внезапно сия тема всплыла в РСГБ.
Помимо уже известных у нас дискуссий, описание опыта Рика K9AO.
I've built a bunch of these as I experimented with them and am happy to
share my experiences.
They work, and they work well. It is a very low noise antenna and
sensitive enough that I do not need a pre-amp on it.
I initially used the KK5JY recommended sizing. I was not impressed with
the gain but it was nice and quiet. Thinking a lot bigger might be worth
a try I built one about 5 times bigger but it was an epic fail as the
noise was much higher. Now, it's important to add that at that huge size
I could not just pick out a quiet spot in the yard, so it's likely not
the antenna but the unavoidable placement near power lines. (I know
others on the LoG Facebook group have built large LoG loops and use them
on longwave successfully.) After that I tried a slightly smaller loop
but elevated about 3 feet and that was a fail too. It needs to be
directly on the ground.
Eventually I wound up with a loop double in size to the original and
directly on the ground. This has worked well for me and I was able to
find not one but 2 spots that are very quiet to place these. So I can
use them in diversity or phase them. I am happy with the performance
from 160 to 40 and it works pretty decently on higher bands too but not
ideal. It's fine on mediumwave but without a pre-amp I don't see any TA
carriers on splits here in Florida. Longwave is pretty deaf but I have
not tried a pre-amp.
I did try using the twisted-pair as a 2-turn loop but performance was
not as good as the single-turn. You'd have to test yourself to see, but
a pre-amp might be a way to get around the smaller antenna gain.
When I heard about the LoG I wanted to test it right away so I went off
to the local building supply store looking for suitable wire. I
eventually decided to mock it up with a spool of cheap solid copper
twisted-pair doorbell wire. That was about the cheapest wire they had
and it was a only to be a test. I found a 500-foot spool and bought
that. I initially thought I'd untwist it and get double the length but
that was impossible, so I just paralleled the twisted wires for the
loop. It's laid right on the ground and held in place with lawn staples.
I didn't have a balun handy or a ferrite core to make one, but as it
worked out I fed it in a different way that I like better. I used the
twisted-pair wire as a balanced feedline and connected it directly to
the loop feedpoint. I ran that as a test all the way back to the shack,
right on the ground, through the door and down the hall and then into
the radio via a small Noelec 9:1 balun I had (not suitable for the
feedpoint in the yard but OK in the shack). At the time I thought this
was an all-wrong way to feed the antenna so if it worked it'd be a
miracle, but I was just testing and couldn't wait to try it so I went
ahead thinking I would have to re-do it later. Well, it worked and
worked very well. One side-effect of the way I feed it that I discovered
later is that it's easy to disconnect the balun in the shack and test
the feredline and loop for continuity. I've had to fix a few breaks from
dogs walking over the wire or mowing and being able to do a quick test
is a big plus. I retrofitted the loop with insulated stab-on connectors
at the feedpoint and a few places along the feedline for isolating for
troubleshooting.
I keep telling myself I'll get some proper stranded wire for the loop
and do something better for feedline like some CAT cable or telephone
balanced line, but the thing refuses to die the way I have it up now.
I'd still recommend a balun in the shack at the end of the feedline. And
that way it would be easy to add in a pre-amp later if you needed it for
certain purposes.
The antenna works a lot better than you might be thinking it would being
directly on the ground. It's a great receive antenna tool to have handy
on the low bands.
73,
Rick, K9AO
