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Re: [TowerTalk] 75ohm cable

To: "'Grant Saviers'" <grants2@pacbell.net>, <Towertalk@contesting.com>
Subject: Re: [TowerTalk] 75ohm cable
From: "Gary Schafer" <garyschafer@comcast.net>
Reply-to: garyschafer@comcast.net
Date: Mon, 19 Jul 2010 17:17:53 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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

> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Grant Saviers
> Sent: Monday, July 19, 2010 3:54 PM
> To: Towertalk@contesting.com
> Subject: Re: [TowerTalk] 75ohm cable
> 
> Lucky you!  I moved and lost my source.
> 
> You can use a coax matching section at the antenna if they are
> monobanders, this works fine and you need a flexible loop anyway.  I ran
> 7/8" CATV hardline 350' to a 2m yagi with a very good match.  The
> calculations are in most every handbook.  The transmitter mismatch
> should not be a problem.  A no tune semiconductor linear may foldback
> with 75 ohms but it would be a finicky one. Any PI network linear should
> work fine.
> 
> This hardline also makes superb low loss broadband dipoles, using the
> shield as the element and the (usually copperweld) center conductor as
> the messenger wire.
> 
> The compression plumbing fittings are the cheapest way to adapt to PL's.
> 
> Grant, KZ1W
> 
> Carol Richards wrote:
> > I am the proud recipent of numerous rolls of 75 ohm, 1/2 in CATV cable.
> Since all of my antennas require 250ft or mor runs this is a real
> blessing. I have a few questions before I start replacing the RG 213.
> >
> >
> >
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> 
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