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[Amps] Trimming the transmission line

To: amps@contesting.com
Subject: [Amps] Trimming the transmission line
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Fri, 12 Oct 2007 18:34:50 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
It did strike me that there is a case where trimming the length of feeder 
affects the SWR.
Let's assume that I happen to have an antenna with a feed point impedance of 
100 + j0. I have an electrical quarter wave of 75 ohm cable, connected to a 50 
ohm cable. Now, trimming the quarter wavelength of 75 ohm cable affects the SWR 
seen by the 50 ohm cable, and if the impedance was something like 100 +j10, one 
could see that trimming the length of the 75 ohm cable produced a reduction in 
SWR.
It's rather a special case, I feel, but shows we perhaps have to be a bit 
careful with blanket statements
73
Peter G3RZP
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