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Re: [TowerTalk] N - clamp style connector

To: "Tower and HF antenna construction topics." <>, "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: Wed, 10 Mar 2010 17:34:23 -0800
List-post: <">>
Well, you've certainly had some experiences there with wild WX!

I've never seen the silver plating actually come off a good N connector, but 
then I've also never taken any direct lightning hits, either.  Maybe the huge 
surge of energy boils off the plating or something, I'm not a metallurgist; but 
I would *think* that if the plating comes off, it has to redeposit somewhere 
else.  The plating is only microinches, so there isn't a lot of it to begin 

However, in 45 years of doing antenna work, I've never seen an unprotected and 
properly installed N connection or splice go bad outdoors, and I've never seen 
the plating "disappear."  I've seen it turn black hundreds of times, but 
normally the oxide protects the base metal very well.

I guess we all go by what we've dealt with; but I've had great luck using N 
fittings outdoors, completely unprotected, and never had one go bad in four and 
a half decades.  After assembly we did only three tests on military cable 
assemblies, under contract from the DoD: (1) Mechanical pull test, it had to 
pass 60 lbs dead hang for 60 seconds; (2) Hipot test, it had to pass 2500Vdc 
with a trip point of 100uA; (3) VSWR test, the assembly had to provide >30 dB 
return loss (when terminated in a standard and rather perfect load) at 100 MHz 
for cables exhibiting <1 dB loss, or 33 dB for cables exhibiting <3 dB loss at 
100 MHz.  That's all we were required to do, and we'd get >95% yields, actually 
very close to 100% on most lots, making thousands of cable assemblies.

73 de Steve WB2WIK/6

-----Original Message-----
From: on behalf of Roger (K8RI)
Sent: Wed 3/10/2010 4:16 PM
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] N - clamp style connector

Steve Katz wrote:
> K8RI: I'm pretty sure those are the ones that turn a rough, dusty,
> bluish 
> green around here. Nickel plate is terrible and silver just disappears.
> That's the main reason I never worry about turning connectors into 
> permanent attachments and use the flooded heat shrink.  IT also keeps 
> them nice and clean. 
> WB2WIK: You know, it's not what the outside of the connector looks like
> that's important.  It's what happens inside.  Using silver-plated,
> mil-spec UG-21D/U type N connectors, I've used them outdoors, completely
> unprotected, for years and years and years even at the seaside when I
> lived on the ocean in central NJ.  The outsides turn very "black" in
> color, but the silver doesn't disappear -- it just develops an oxide
> coat, which actually protects the connector as soon as it happens.
I don't worry about them while they're "up there", but normally these 
refuse to come apart with the nut becoming a permanent part of the body 
on the shiny ones.  All of the silver plated ones, at least on top of 
the tower end up with no plating left. They are just green brass. IF 
they come apart they squeal as the nut is turned out taking a good 
portion of the threads with them.  I normally use "N-type" for the 
weather proofing as most of the external stuff is gone within a year or 
two and bare UHF connectors provide no weather proofing. The MMM flooded 
heat shrink is about the only stuff that has managed to stay, but it 
hasn't had a real work out with lightning.  The first 5 years the tower 
took 3 visually verified, direct hits each year. It's only taken two 
since then. How many unverified hits? Who knows, but I thought for a 
while I had a lightning magnet.  Since installing the elaborate ground 
system and grounding the coax shield at the top and bottom of the tower 
I've had no damage to any equipment or coax even with all those hits. 
Connectors "up there" look pretty ratty but are still working.

BTW, after one storm I found some large pieces of tape and coax seal in 
the yard. They looked a lot like expanded metal. So tape and seal in 
hand, or rather, pocket I headed up the tower.  There I found all of the 
connectors were bare metal. Most were clean brass that appeared to be 
etched, but absolutely no silver plate left on N or UHF. IIRC I had to 
throw away one of the UHF connectors as it had to be cut off the coax.  
I couldn't get them apart. At least I didn't find any water in the 
coax.  I replaced the coax seal and tape.  They were still working about 
7 years later when the new tower went up.

Oh! a while back I had to get started on replacing the pigtails at the 
top.  Only one connector out of the 5 cables would come apart. I had to 
cut all of the others off and no these were not filled with epoxy<:-)) 
But they were thoroughly weatherproofed with the MMM heat shrink.  All 
connectors were still shiny, but  neither UHF nor N would budge.  I 
didn't cut any of them apart, but they acted like the threads were 
welded...or gauled(sp?).


Roger (K8RI)

> After several years of direct exposure I've unscrewed these fittings and
> found everything underneath to be shiny and dry.  I've absolutely never
> seen one take in a drop of water (unprotected) if it's the right
> connector, installed on the right cable, so they are compatible.  
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