I am curious how you grounded the driven element with a torroid? I can
understand grounding the reflector and last director but does grounding the
DE add much loading when shunt feeding?
If you are seeing a big decline in signal when feeding both beams, perhaps
you have an issue with the relays, impedance transformer, etc. How is the
phased SWR? I assume both antennas are fed with the same length coax.
John KK9A
Stan K5GO wrote:
A little dilemma - I just put up another tribander at ZF9CW on my new tower.
I originally had two smaller tribanders on a separate tower. I had built
two identical chokes and they have another torroid across the feedpoint that
would electrically ground both sides of all three driven elements to the
boom for additional top loading for my 160m shunt feed.
When I took the smaller antennas down I did a little work on the balun -
re-soldered some connections, etc. I don't think I changed which side of
the element the center conductor would be attached to but cannot be 100%
positive.
Now, I decided to make another large tribander and built a swing arm so I
can rotate it and have the other balun on it. I know I didn't change that
balun. The antennas are at 78 and 47 feet. I am seeing some S Meter
readings when switching between, upper, lower, both that make me wonder
whether I actually have them 180 degrees out of phase instead of in phase.
I could add an electrical half wavelength of coax for one band and evaluate
it over time, with and without that extra coax in line with one antenna and
try to determine what I've got. Would it be good enough to call CQ on 15m,
look at the RBN for JA spots and then insert a half wavelength of coax for
15m and do it again comparing the results and assume that in phase would be
the better of the two?
I don't want to do what would be necessary to reach the balun on the top
antenna which is out about 8 feet. That choke across the feedpoint makes it
impossible for me to just use a piece of aluminum tubing as an extended lead
from an ohm meter to tell what is what. I could more easily tilt the lower
one up and get to the balun to change it if I knew for sure they were
currently out of phase.
What I'm looking for from the experts is the best way to determine whether
these antennas are in phase or out of phase without a lot of guesswork or
info on how I could best flip the phasing 180 degrees for all three bands.
I would not necessarily know which was which but have the ability to flip it
180 degrees from wherever it currently is.
Thanks.Stan, ZF9CW
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