Phasing will have no effect but I am not sure why you would change the coax
length. If the 6m beam is 90 degrees to the C3 and the 6m boom length is
around 1/2 wl on 20m or less than that but electrically 1/2 wl due to
grounded elements there will be serious interaction.
John KK9A
To: "towertalk@Contesting.com" <towertalk@Contesting.com>
Subject: [TowerTalk] Interaction Issues
From: Jeffrey Cantor <k1zn@att.net>
Reply-to: Jeffrey Cantor <k1zn@att.net>
I recently had some tower work done. Ihave a Rohn 25 tower up 60 FT. I
have
a C-3 and a 6-element Cushcraft 6Mon it. Both antennas were doing fine -
SWR
essentially flat on the C-3and around 1.5:1 on the 6M. They were both
mounted
on a 9 FT mast,separated by about 6 FT. The job was to replace the 9 FT mast
witha 15 FT lighter mast and to install a new 12/17M WARC Cushcraft antenna.
The new setup had the 12/17M antenna atthe top of the mast; the 6M in the
middle, phased at 90 degrees to the otherbeams - - separated by roughly 6 FT
between it and the lower C-3 and the WARC. After the install, I am noticing
a
2.0:1. 2.4:1 SWR on the C-3 on 20M only; 15M & 10M are OK. On the 6M -3.0+
SWR. Do I have an interaction problem betweenthe 6M and C-3? Should the 6M
be
at the top of themast? Offset to the others, or not? Jeff/ K1ZN
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|