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[TowerTalk] four square array tuning

Subject: [TowerTalk] four square array tuning
From: Steve Bookout <steve@nr4m.com>
Date: Mon, 28 Nov 2016 17:27:52 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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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