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Re: [TowerTalk] RG-149: 50 ohm/70 ohm - does it matter?

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Subject: Re: [TowerTalk] RG-149: 50 ohm/70 ohm - does it matter?
From: Steve Hunt <steve@karinya.net>
Date: Mon, 16 Dec 2013 10:22:38 +0000
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
That's right - and it doesn't have to be that close to a 1/4 wl or odd multiple to be a problem.

If you feed a 50 Ohm load through a 75 Ohm line, any line length from around 0.15wl thru 0.35wl (or repeats) will give you an SWR(50) of 2:1 or greater. That's enough for the protection circuitry in many radios to beginning backing off the output power.

Steve G3TXQ



On 16/12/2013 00:21, Richard (Rick) Karlquist wrote:


If you are driving a multiband antenna, it is actually
quite likely to have near a 1/4 wl on some frequency especially
if you have a few hundred feet of coax.


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