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From: Graham Sharp
Subject: Re: How to check for a 50 or 75 ohm connector
References: <email@example.com> <firstname.lastname@example.org> <3E077496.EDFF8BE0@sympatico.ca>
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Date: Tue, 24 Dec 2002 17:15:02 +0000
NNTP-Posting-Date: Tue, 24 Dec 2002 17:17:26 GMT
Organization: ntl Cablemodem News Service
On Mon, 23 Dec 2002 15:39:50 -0500, Dave Holford
>> F connectors leak RF in and out like a sieve. One of my old colleagues did
>> extensive tests of 'transfer impedance' (this has nothing to do with
>> characteristic impedance, but is a measure of screening) and could find
>> nothing under the sun that had worse screening than an F connector.
>While I am totally unimpressed by "F" connectors and would never use
>them if almost anything else could be used, I have some difficulty with
>the leakage stated above.
Agreed, but I found that to get leakage down to decent levels, the
connectors have to be 'nipped up' by about 1/4 turn with a 7/16"
spanner. Finger-tight is not enough. (This was with crimped
connecters, not the nasty screw-on type.)
>If that is true I find it unlikely that their widespread use would be
>permitted in the vicinity of airports since cablevision systems commonly
>utilize frequencies used for aviation communications and navigation
>systems; and the prospect of all those connectors leaking RF at
>frequencies used for Instrument Landing Systems would pose a very real
>hazard to aviation safety. I can think of several locations where large
>housing complexes and apartments lie within 1 mile of an ILS system and
>no problems have ever been experienced with either localizer or glidpath
I have used "F" connectors several airports with no adverse
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