<<<AND because they don't have to LISTEN on that antenna.>>>
Well, no one should be using a vertical antenna for receiving,
especially on 160 and 80 m. They are usually untenable in cities and
suburbs.
<<<Right, but few hams have great radial systems for 160M, and most
hams don't live in the middle of nowhere where there's no local noise.
A choke matters when there are a few radials, short radials, elevated
radials, etc. N6LF has done extensive research, both modeling and
measurement, on radial systems. One of his results is that with a few
radials, balancing current between them has a strong effect on losses,
and a combination of radials and an earth connection is a bad thing.
Use of a feedline choke is a good thing in that sort of antenna
system.>>>
My work has not shown this to be true. I am in a city on a 50 x 100
foot lot. I have had an enormous plasma TV about 25 feet from my
antennas. You have not experienced noise on 160 m. until you have
heard a plasma TV. I have worked with feedline chokes and found that
from the stand point of RF on the line they do nothing. I have a
compromise ground system of 101 radials. Some are only 10 feet long.
If a ham wants to put down an incomplete ground system and resort to a
coax choke and live with poor antenna efficiency that's his
prerogative. I DO have a relay in my inverted L feedline that breaks
both coaxial conductors on receive. At my location I found that is
necessary to avoid detuning the receiving antennas. Also, I
specifically confined my comments to at or below grade radials; not
elevated. That's a different matter. I'm familiar with N6LF's
modeling work. My experience is that modeling is interesting but not
the last word. Real field test observations on site, and data from
antenna range testing and measuring are decisive. Anything else is an
estimation, albeit worthwhile depending on the software and number of
parameters. No modeling is a substitute for on-site tests with real
antennas.
The original question had nothing to do with a multi-operator
multi-transmitter contest situation. For local noise reduction the
best thing I've found is a phasing network and a pair of rx antennas
appropriately spaced. By the way, it amuses me when I read about 160
m. DX chasers bemoaning their existence as weak signal ops, as if a 5
second CW or FT8 599 exchange is the hardest thing out there. They
ought to try sustaining copy of a piss weak low modulation AM operator
over an hour or two, someone with a dipole 20 feet high.
73
Rob
K5UJ
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