[TowerTalk] Isolating adjacent 4-Squares
k3lr at k3lr.com
Sun Dec 20 22:34:37 EST 2020
This is going to be tough with all of these wires so close together - to
make both bands work right. Elevated radials further complicates the
problem..1/4 wave shorted stubs on the 160 elements is not going to help 160
- it might help 80 (it did here).
You might try disconnecting the 80 meter feedlines at the feed points of the
80 meter elements and see if 160 comes to life. If not, remove the 80
completely and see if 160 works. If not, you will need to detune the towers.
With elevated radials - everything is in play and you have bigtime coupling
between the two antenna systems.
Having high CMI chokes at the feedpoints of all elements is needed to keep
the feedlines out of the picture.
You will need to experiment - trying one thing at a time.
Good Luck, Merry Christmas and 73
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
Sent: Sunday, December 20, 2020 12:23 PM
To: TOWERTALK at contesting. com
Subject: [TowerTalk] Isolating adjacent 4-Squares
I have an 80M wire 4-square around tower #1. (90ft with two big 10M & 15M
monobanders) Each vertical has 12 above ground radials and is tuned to
3535. All guys are broken with insulators.
This array works well.
My second version of a 160M wire 4-square around tower #1 was raised last
week. They are Inverted L's to a 120ft tower. It already has two Cushcraft
40-2CD's and a big homebrew 20M6L OWA yagi. All guys are broken with
insulators. Each Inverted L has 20 on-ground radials and is tuned to 1725.
The closest 80M element is 40 feet from a 160M element.
The 160 is not working well. I will be testing the phasing lines once this
snow melts. ###
I want to apply a passive device to further isolate these systems. I'm
thinking of a 1/4 wave 50 ohm shorted coaxial stub on each feedpoint. My
first guess is the 160 elements.... ?
Alternatives are to move one of the arrays.... but I'd rather explore
making them work where they are.
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