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Re: Topband: 50 ohm direct burial coax cable

To: <topband@contesting.com>
Subject: Re: Topband: 50 ohm direct burial coax cable
From: "James Wolf" <jbwolf@comcast.net>
Reply-to: jbwolf@comcast.net
Date: Fri, 13 Jun 2014 17:03:52 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
This does however, slightly narrow the bandwidth of the antenna if the coax
loss is small because as you move away from the perfect 1/2 wave point the
coax will start to show SWR.   For monobanders this usually isn't a problem,
but it may be for some tribanders.

This will also work on all the non-WARC bands.   For Tribanders, if you cut
the coax for 1/2 wave on 20 or 40 meters, make sure you tweak it for
multiple of 10 meters, which will be a more critical measurement.  The rest
of the in-between bands should fall into place. 

>>> You can easily make the 75 ohm coax essentially "invisible" in a
monoband application by using some RG-11 to extend the total length of the
75 ohm feedline to any multiple of 1/2 wavelength. 

Jim - KR9U



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