At 08:12 AM 10/9/2006, Dave NØRQ wrote:
>Or, even on a vertical with elevated radials, if there are "enough"
>radials, does it really matter if the feedline acts as just one more
>radial?
>
>On my 40m vert, there are about 20 elevated radials, about 10'
>above ground, and the feedline also comes out at about the 10'
>level. Since the feedline is about 200' long, is feedline radiation
>really an issue in this case?
Only if you are obsessing about making the
vertical performance match a theoretical model.
There IS a potential problem with the "coax as
just another radial" and that is that since the
coax usually goes places radials don't, you might
get RF in places you'd rather not have it. And
that goes both for RF radiated from your antenna
or for interference that winds up IN your feed system.
I had a problem with what appeared to be RFI from
a network cable coupling to the outside of a coax
line and then into the antenna. Cat 5 wire and
coax were bundled together going up to the
roof. I did away with the network cable, and all
was better. Didn't bother to track it down any further.
I suspect that some RFI filtering would solve
this sort of problem quite nicely, and I have a
box full of nice lossy toroids now.
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