On 12/30/2013 2:56 AM, Jim Thomson wrote:
Date: Sun, 29 Dec 2013 16:13:06 -0700
From: "Jim Garland" <4cx250b@miamioh.edu>
To: "'Ian White'" <gm3sek@ifwtech.co.uk>, <jtml@vla.com>,
<amps@contesting.com>
Subject: Re: [Amps] "N" Connector
I've had bad experience with N connectors on long runs of coax in the
wintertime. My theory, unsupported either by other facts or long
deliberation is that the coax length shrinks slightly at low temperatures
and tends to pull the center pin out of its making connector. The early
symptom is always an intermittent loss of receive sensitivity, but in really
cold nights I've lost transmit continuity as well. Personally, I don't care
for N connectors (at least at HF frequencies) but in the olden days when I
was using lot of military Transco coax relays and motorized coax switches
there wasn't much of an alternative.
73,
Jim W8ZR
## You just nailed it. Part of the problem is there is a lot of different
type of N
connectors out there.....with and without pasivated center pins. The non
pasivated
types would allow for the center pin to slide back a tiny bit....when its cold
out.
That’s when the int RX and in extreme cases, TX problems started up.
Except the only ones I've lost were in the summer. They were in the
feed lines to 75 meter sloping dipoles (Near the East end of the shop)
with very high SWR and resonant near the bottom of the band. These were
on about 60 to 80 feet of LMR-400 which really would swing in the wind,
particularly where it funnels between the garage and shop and trees.
One lead to a 40 meter, sloping dipole (near the West end of the shop,
with UHF connectors blew against the edge of the shop roof and wore a
hole through a piece of original 9913.(the edge of shingles are better
than a rat tail file <:-)) ) I didn't think it could get that far over,
but the swr went up and when I took the connectors apart in the shop the
water came running out. It was LMR-400 beyond the connectors so the
water could go no farther. I thought I'd gotten rid of the 9913, but
that piece escaped. Anyway that's the kind of movement those leads get.
The failed N connectors were shorted, but the pins showed no signs of
heating. One was a double female. Lightening? I didn't lose any on
the other antennas, but could be.
That was the only antenna that I had connectors fail on. The center
fed, 75 meter sloping, fan dipole is in the back yard and it does not
have N-connectors.
Ive still not found a source of 7-16 DINs at a reasonable price
I do have some UHF connectors for the LMR-600, but I've had a number of
them physically break.
73
Roger (k8RI)
## I gave up on Type N..and switched to 7-16 DIN. Back in the mid 80s,
Andrew
stopped making UHF connectors for .875 inch heliax. The only choices left
from Andrew
is type N...and 7-16 Din. Up until a few years ago, the telco where I worked
at..used
these huge type N connectors on 1.25 inch and 1.625 inch heliax. They are the
size of a
coffee mug.... complete with this stupid tiny center pin. They really look
stupid when you see
them. They also have to be carefully installed...and manhandling coax that
big is no fun.
Gotta been careful so the center pin does not get damaged. Normal deal was
to reduce down to smaller
coax for the last few feet, where it plugs into the various pieces of cell gear.
The center pin on a type N is the same size as the pin on a BNC connector.
## The telcos and cell companies have all switched to 7-16 Din. Type
N...good riddance imo.
The 7-16 din for bigger coax cables is the same or not much more $$ vs type N
anyway.
As far as I know, Andrew still makes uhf connectors for their .5 inch coax.
later........ Jim VE7RF
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