[CQ-Contest] Adding 80m Shunt feed w/160

Stephen M. Murphy murphys at comcast.net
Mon Nov 15 15:54:22 EST 2004


Have you tried tapping it lower? I'm probably wrong, but 50-60' seems kind
of high for an 80m tap on that tower...

I'm building a pair of 40m verticals using the TT tubing.  Not sure what
info you're looking for, but the tubing I got from them matched the specs in
their catalog and I don't see anything to complain about as far as quality
is concerned.

73-GL,
Steve N8NM

----- Original Message ----- 
From: "Scott Bauer" <w2lc at ix.netcom.com>
To: <cq-contest at contesting.com>
Sent: Monday, November 15, 2004 12:51 AM
Subject: [CQ-Contest] Adding 80m Shunt feed w/160


Has anyone out there combined an 80m shunt feed on a tower that already has
a shunt feed for 160m ?

I have an 76 foot tower, with a 160m shunt feed, with the shunt wire
connected at about 60 feet.  It works very well for me on 160m, or at least
it seems to.  I only run 100W on 160m, since my amplifier does not have 160.

I tried adding an 80m shunt feed, first with the shunt wire connected at
about 50 feet, which didn't work then moved it to 60 feet, which also didn't
work.  I am using an L network, with a shunt roller inductor and a series
variable capacitor to the shunt wire.  I have more than enough inductance
and capacitance to work with, both value and tuning range.

The 160m shunt feed took all of 30 seconds to tune.  On 80m I can't even get
it close.

The tower has a PRO-67 on top at 77 ft (40m thru 10m), with three other
yagis at 64, 50 and 37 feet, and an 80m dipole.

Since the dipole I have on 80m doesn't seem to do well, I want to shunt feed
the tower on 80m and take advantage of the radials already installed for
160.

The only other option is to buy tubing and make an 80m vertical and put down
another set of radials.  Anyone have experience with the tubing that Texas
Towers sells ?  I don't really want to use irrigation tubing, looks like it
is harder to support.

Thanks in advance for the help.

73 Scott W2LC





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