[TowerTalk] Thanks all... N or UHF?

K8RI on TowerTalk K8RI-on-TowerTalk at tm.net
Tue Oct 17 20:28:31 EDT 2006

Thanks for all the input on the N Vs UHF.
I think there was a lot of information that wasn't in the archives.

The reason for the question, as I think I stated, was to decide on which 
type of connectors to use at the top and bottom of the tower where the 
shield is grounded to the tower. I've seen relatively neat grounding straps 
made to go over the shield of the cable to directly ground it to the tower 
leg and several have mentioned that here as well.  I'm not that neat and 
have an adversion, whether well founded or not,  to cutting the jacket 
except for connectors.

I've been using a mixture of N and UHF connectors with Ns for 6 and up. I've 
also used them on the feeds to the ferrite chokes on the 75/80 meter center 
fed half wave slopers.  Suprisingly I lost an N type barrell connector 
between the coax and choke to one of the slopers.  The thing is a dead 
short.  That is the only N-type connector I've lost in that manner.  OTOH I 
have lost several N and UHF connectors at the top of the tower due to 
mechanical failure.

It appears that the top of the tower (and up) is a rather hostile 
environment.  Brass, copper, and silver end up with a heavily *etched* 
appearance in just one season. Silver will be white. Connectors bind, or 
gall which means disassembling a connection will destroy both connectors. 
Forget about takeing a connection apart that has been up there a couple of 
years or more. Tape, coax seal, and liquid electrical tape help, but they 
too suffer short life spans, but I'd rather replace tape and coax seal than 
connectors at the top of a 100 foot tower.

I'll start by saying the way I treat/use coax connectors they are a one-shot 
deal be they UHF or N.

As some have pointed out and I can verify, N-connectors are not water proof 
unless you are very lucky.  Perhaps that is why the Amphenol connectors come 
with a 3" long piece of flooded heat shrink.<:-))  So, all my connectors, be 
they N or UHF get installed with flooded heat shrink tubing along with 
liquid electrical tape.  This combination has worked very well for me. 
I've also used a bunch of the newer N-type that go together like UHF 
connectors. I treat these and UHF as if they were an open connection to the 
weather (which they are) and use liberal amounts of liquid electrical tape 
and heat shrink tubing.  I would add that N-type are not *necessiarily* 
mechanically stronger than UHF either.

When I assemble N-type connectors as a last step I back out the compression 
nut and pour in about a half dozen drops of catalyzed Vinyl Ester resin. 
This effectively turns the connector, jacket, dielectric, and braid into one 
piece that is not going to come apart.  As I'm doing a lot of fiberglass and 
carbon fiber work in the shop I have a lot of this stuff around. I find it 
works much better in the connector application than epoxy as it has a far 
lower viscosity as well as better electrical characteristics.  When the 
connectors are ... well... connected up on the tower I put a sleeve of 
flooded heat shrink over them. A coat of liquid electrical tape first will 
make the heat shrink easier to remove later as that flooding compound is 
really "hot glue". Hot clue comes off the liquid electrical tape a lot 
easier than it does the bare metal.  I let it *bond* to the coax jacket.

Sooo... based on the above and the input from the group I'll *probably* cuts 
some strips of flashing copper, make the coax connections at the top and 
bottom of the tower using barrell connectors. Wrap the barrel connectors and 
tower leg with the copper flashing and clamp the whole works together using 
SS hose clamps torqued down tight.  The Andrew connectors are solid brass 
and long enough to make this an easy proposition. BTW the center pins in the 
Andrew connectors are captive.

Again, thanks for all the input.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2

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