If the exercise is simply to find that particular length then calculate at
what frequency it is a 1/4 wave using the published velocity factor. Cut it
a few percent longer.
Then short one end and connect the other to a noise bridge or directly to a
receiver. Trim until the deepest null is at that exact calculated frequency.
This removes the tolerance unknown of the cables velocity factor.
Unless you have a VNA or other lab equipment the above will get you as close
as possible. Ive used this method for decades to cut phasing lines for yagis
and verticals as well as harmonic stubs and have never been dissapointed.
----- Original Message -----
From: "Tom Osborne" <firstname.lastname@example.org>
To: "Towertalk" <email@example.com>
Sent: Wednesday, October 17, 2007 12:46 PM
Subject: Re: [TowerTalk] Figuring degrees of a coax line
> Hi Roger
> I am trying to put up a new phased vertical array for 40 meters.
> The 84 and 71 degree lengths are the ones in the Low Band DX'ing book.
> According to the directions, 84 and 71 degrees will give more gain and FB.
> Tom W7WHY
>> Hi Tom...
>> What, exactly, are you doing? As Frank mentioned, a 71 deg length of
>> coax terminated in its characteristic Z is not necessarily 71 deg when
>> terminated in some other Z.
>> 73, Roger
>> Remember the USS Liberty (AGTR-5)
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