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[TowerTalk] Connector insertion loss

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Subject: [TowerTalk] Connector insertion loss
From: (Ian White, G3SEK)
Date: Tue, 2 Sep 1997 07:24:40 +0100
Rod Fitz-Randolph wrote:
>I truly believe that, if you have a several hundred foot run of coax
>like I do, that regardless of whether or not there is an annular ring or lip,
>when the center conductor of the coax retracts by as much as a 1/4", something
>will give!

Surely it depends on the installation? If the coax has a loose inner
conductor but contains some bends, most of the expansion/contraction
forces will be taken up by flexing at the bends, the cable acting like a
spring. If the coax has a fixed inner conductor (as in foam heliax) the
forces are distributed all the way along the cable so there is much less
relative movement at the ends.

The worst case would be a straight drop of several hundred feet down a
tower (which is common in commercial installations) and a cable with a
loose inner conductor. In that case the forces will have nowhere else to
act except the connector pins, and ordinary captive-pin N connectors
probably won't save you from the consequences of having installed the
wrong kind of cable. 

My impression is that captive-pin N connectors are rather rare in the
USA compared with the original MIL type. They are quite common in Europe
and experience has generally been good. The RG213 size generally has a
much better braid termination and cable clamp as well, all of which
helps to keep the connection reliable.

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)

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