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Re: [TowerTalk] 75 ohm - v - 50 ohm coax

Subject: Re: [TowerTalk] 75 ohm - v - 50 ohm coax
From: Steve Hunt <steve@karinya.net>
Date: Mon, 18 Feb 2013 13:38:14 +0000
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
If the antenna has an impedance of 50 Ohms, and the coax is close to a quarter-wave or odd multiple long, you'll see an SWR(50) of 2.25:1 at the shack end instead of 1:1.

73,
Steve G3TXQ



On 18/02/2013 13:03, John E. Cleeve wrote:
Good afternoon gentlemen,

A 100 metre(325ft)drum of 75ohm, 25mm(1 inch) diameter coax, and the
appropriate connectors, has been donated to my GM project, for which I am
very grateful.

I am considering using this coax as one of the feeders buried to a
distribution point out in "the aerial field". My question is, from the
groups experience, would I notice any serious difference in the aerial
matching etc, between the use of 50 ohm and 75 ohm coax at HF.

I have yet to set up a practical experiment, to measure the loss etc.
using differing resistive terminations, but that will be done when the
cable is unwound, before the cable is installed.

I would appreciate your thoughts/experience.

Sincerely, John, G3JVC/GM3JVC.

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