Hi Steve,
You need to OPEN the unused radiators while you adjust one at the time!
If connected to ground they couple to the radiator in tune.
73
Peter, DJ7WW
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Steve
Bookout
Sent: Montag, 28. November 2016 23:28
Cc: towertalk@contesting.com
Subject: [TowerTalk] four square array tuning
Hello all,
Over the last few years, I have added four square arrays for 40 meters
and 80 meters, and both work really outstanding.
Recently, I added a third one for 20 meters and am having a difficult
time with it.
Short version is I resonated each antenna individually, with the others
shorted with clip leads to gnd, to 13.9 MHz +/-. The array, as a whole,
doesn't show a suitable SWR until 15.6 MHz! Like the others I had
installed, I was expecting a 150 KHz, or so, rise in frequency to
resonance. I do understand that it's really all about the power being
dumped to the dummy load, but the amp is not going to tolerate a 3.5 to
1 SWR.
Cables were cut using an AIM antenna analyzer and were double checked.
All other cable/parts were checked out and shown to be correct.
80 ground mounted radials under each antenna.
Built just like I did the other two.
Gonna look at it with an O-scope tomorrow and check phase vs freq. My
gut feeling is an incorrect value component.
My gut feeling aside, I would appreciate any ideas.
73 de Steve, NR4M
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