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Re: [TowerTalk] N - clamp style connector

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] N - clamp style connector
From: "Steve Katz" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Thu, 11 Mar 2010 07:57:55 -0800
List-post: <">>
Steve Katz wrote:
> As someone who's actually set up assembly lines to install Type N
> military connectors for USAF contracts (20+ years ago!), I might add
> of the biggest problems hams have is misapplication of connector vs.
> coax.  Even a skilled expert who's assembled thousands of N connectors
> on cables is going to be highly challenged if the right materials
> presented to him.
> As an example, I see a lot of hams using the UG-21D/U connectors from
> the Amphenol "RFX" series (82-202-RFX or equivalent).  You might note
> those are intended for "RG8, RG9, RG213, RG214" cables.  Well, this is
> downright impossible.  RG8 and RG213 are single shielded and smaller
> O.D. than RG9 and RG214 which are double-shielded.  For a "clamp"
> connector, how can a single design work for cables having either one
> two shields, and having two different O.D.s?  Impossible.
> So what Amphenol did, in their infinite wisdom, was make the connector
> suitable for double shielded cable with a larger O.D., and figured
> somehow we'd make that work for the other stuff.  It really doesn't.

Isn't that why there's little funky rubber/silicone grommet looking 
things in some installation kits. I always figured they're to make the 
cable "thicker" so it fits the connector.

::Yes, a standard N connector includes a rubber gasket; however that
often can't do the job if the cable O.D. is too small for the nut and
the gasket.  RG214/U almost always works fine and seals
watertight/gas-tight.  But a lot of us are using stuff like 9913, LMR400
etc. which is actually undersized cable with a thinner vinyl jacket than
found on RG214/U.  Although these new "low loss" cables are double
shielded, the first shield is a very thin layer of aluminum-mylar foil
that isn't nearly as thick as the woven plated copper braid of military
cables, and there's no way to peel the foil back, it remains
inside the hole of the clamp and doesn't contribute to the clamping.
The rubber gasket compresses until it cuts itself in two (which is
actually supposed to happen) but it cannot compress enough to fill the
void between the cable and the nut.  Not only isn't this weatherproof,
but it's not even mechanically strong and these connectors can often
just be pulled off the cable with 20-30 lbs of force -- not very much.

We can "touch up the X-Rays" by using tapes and shrink tubing and all
sorts of stuff, or we can simply use the right components in the first
place, which don't require any of these remedies.


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