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Re: [TowerTalk] 75ohm cable

To: garyschafer@comcast.net
Subject: Re: [TowerTalk] 75ohm cable
From: "Rick Karlquist" <richard@karlquist.com>
Reply-to: richard@karlquist.com
Date: Mon, 19 Jul 2010 18:26:27 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Gary Schafer wrote:
> You can have up to a 2:1 mismatch (SWR) at the transmitter using 75 ohm
> line
> if the antenna is a flat 50 ohms. If your 75 ohm line happens to be a
> multiple of a quarter wave length that will transform the 50 ohm load to
> 100
> ohms seen at the transmitter end.
>
> 73
> Gary  K4FMX

Actually, the transmitter mismatch will be 2.25:1 (112.5 ohms).
Additionally, if the "50 ohm" antenna is actually 33.3 ohms,
it would be a 1.5:1 VSWR with 50 ohm coax but 169 ohms
with 75 ohm coax.  Your 50 ohm  transmitter (or tuner) would
effectively be working into a 3.4:1 VSWR.  This may or
may not be OK.

Rick N6RK

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