Hi:
That could be DON'T USE A 80M DIPOLE ON 160. I put up some dipoles for the
PAQSO party and I wanted something better than a 80m dipole and a tuner on
160m. So I put up a fan dipole with one of the dipoles a loaded dipole
(shortened to 200') for 160m.
Before I did that I had one of my local friends look at my signal strength
on my 80m dipole and tuner.
The new antenna was resonate with low SWR in the part of the band used by
the PAQSO party and when we did the same check, the new antenna was 25db
stronger. Why was that? Modeling the 80m dipole on 160m, it showed a Z of
9.2-J1127 Ohms at 1.85MHz. Using the program TL with a 9913 type feedline at
a length of 135' showed an excess loss due to the high SWR of 14.5db. Then
going to the tuner part of the TL program it calculated a loss of 6.8db
through the tuner for a total loss of 21.3db through the system. This is
very close to what we measured, completely in the within the margin of error
of the simple measurement like we did. More importantly I could hear band
noise that I could never hear before. Feeding it with open wire line would
have worked much better as the excess loss in the feed line would have be
1.8db with 5.2db loss in the tuner for a total loss of 7.01db. But with my
loaded dipole I need no tuner in the part of the band I operated in. The
losses in the loading coil are about 1db so my total system loss is less
than 2db, which is better than a 80m dipole and tuner, or even one feed with
open wire line and a tuner. It just shows there are no free lunches in
antennas and every chouse comes with a cost, in my case it's bandwidth and
loss in loading coils. I looked at the various kinds of antennas I could
use, picked what would work best for me.
--
John Passaneau, W3JXP
Penn State University
"Cecil Moore" wrote in message
...
Reg Edwards wrote:
The moral is - DON'T USE A G5RV.
Specially one with any coax in the feedline.
If you've bought one, you've been robbed.
It's a pretty good antenna for 80m, 40m, & 20m. My web page shows
how the "matching section" gives a pretty good match to coax on
80m and 40m. Mine also worked well on 12m.
--
73, Cecil http://www.qsl.net/w5dxp
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