[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
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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