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RE: [TowerTalk] RE: [Antennas] coax 'sweet lenght'

To: "'Chris Boone'" <>,"'FireBrick'" <>,"'TowerTalk List'" <>,"'Antenna List'" <>
Subject: RE: [TowerTalk] RE: [Antennas] coax 'sweet lenght'
From: "David Robbins K1TTT" <>
Date: Mon, 11 Oct 2004 13:58:13 -0000
List-post: <>
> ANY feedline repeats the Load Z (Impedance) every
> 1/2wavelength..remember that must take into account the velocity
> of the feedline...for normal coax its about 66% so 0.66 x 468/freq in
> MHZ = length of 1/2 wl coax at that freq...the only thing about this
> you can use ANY feedline bewteen radio and antenna as long as its 1/2
> and the radio will match the antenna (if the antenna is 50ohm +0j
> already)....SWR at the radio will be accurate.....if the antenna is
> 50ohms or has reactance, the feedline will always cause a WRONG SWR
> reading at the xmtr unless it is a 1/2 wl (in coax)..

wrong.  The swr in the coax doesn't change with length, except for small
losses that always reduce it.

The problem is cheap meters or installations that have rf on the outside
of the coax... again, a metering problem.  The swr does not change with


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