I've had the same experience as Roger. Decades ago I started to convert to
N-series connectors, but started having problems with the non-captive pins
pulling out in cold weather.
I have gone back to the UHF-series connectors and no problems since.
N-Series might be important for VHF/UHF connections, but I find that the UHF
connectors have worked fine for my HF and very occasional 6-meter work.
73, Bob - W3YY
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Roger
(K8RI) on TT
Sent: Monday, November 17, 2014 9:00 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Some advice about crimp ;type coax connectors
On 11/17/2014 10:56 AM, Gary J - N5BAA wrote:
Caution: N-Type connectors may not be your answer.
I crimp nearly all coax connectors here as well, but went back to UHF
connectors on all vertical runs on the tower as well as sloping dipole
feeds.. N-type connectors have a problem and it can be a big one on
vertical runs. On most N type connectors the center pin is not captive.
The weight of the coax center conductor can cause it to migrate down, taking
the center pin with it, either creating a poor electrical connection, or
none. The same problem exists in center feeding half wave, sloping dipoles.
When the temperature is well below freezing, or even below zero is not the
time to find out you have this problem.
The problem can be reduced with a 360 degree loop in the coax immediately
after the connector, but not so close as to induce leverage into the
connector. I have also resorted to using a strong 2-part epoxy to pot the
coax in the connector "with good success".Leave a space between the back end
of the center pin and the dielectric. Completely fill this area with epoxy.
Use a good, high quality epoxy that has a high resistance when cured. It
likely will have a much higher dielectric constant than the coax, but such a
small area will not be noticed at HF and VHF. It also needs to have a high
breakdown voltage. Don't use a low viscosity (thin, or runny) epoxy and do
not get any on the mating surfaces of the connector. It works, but can take
time to install properly (needs to thoroughly cure before coax installation)
and is easy to make mistakes. I've done a lot of epoxy work so I'm
comfortable with it, but it might be a bit much for the inexperienced.
With a 100' 45G this became a major issue which raised other issues. I went
from LMR400 to LMR600 on the vertical runs. (not the sloping dipoles).
Sticker shock is quite descriptive of the price for UHF connectors that fit
LMR600. I prefer DIN 7-16 connectors, but they cost more than the UHF for
LMR-600.
As LMR600 is larger and heavier, the center conductor migration on vertical
runs is worse than on LMR400. Some inexpensive LMR 600 UHF connectors may
easily break off with very little applied leverage. That
360 degree loop needs to be far enough away from the connector that the
cable can be held to make the loop with out applying leverage to the
connector. Also make the loop large enough that there is no side force
applied to the connector when the loop is taped to the tower.
Here in the North country (Michigan) with our major temperature swings from
highs in summer to lows in winter the expansion and contraction makes this
problem even worse.
I had nearly all vertical runs fail at the top N-Type connector on the 45G
the first winter they were up.
I also had the connectors fail from nearby lightening strike. So far, I've
never had a UHF connector fail from that.
I had a double female connector in a splice to a 40M sloping dipole fail.
Looks goos. Shows good with an ohm meter, but is shorted at 100W of RF.
73
Roger (K8RI)
> I crimp all my coax connectors now too, and horrors upon horrors made
> the jump from UHF Pl-259's to Crimp N connectors at the same time. I
> made the change to N connectors because I was buying new crimp
> connectors anyway and it made sense to change to the much better
> connector at the same time. The next time I am inside my Elecraft K3
> and P3 I will change out the SO-239's for female N connectors, and
> until then I just use adaptors. I must admit I am probably not a
> "Real Ham Operator" since I am not a good solderer. I can manage to
> solder the N pins though. I say all the above with trepidation
> though, as recently on our club reflector I started a UHF vs N and
> solder vs crimp war that has resulted in one of our club members
> resigning his membership. Being a 3 year ham, I had no idea that the
> opinions on connectors ran so deep.
>
> Is there a source for just the crimping dies for Power Poles that
> might fit in my crimpers?? My crimpers came from below - they are the
> same as 90% of the crimpers out there and buying here gets you two
> crimper pliers vs one crimper and two sets of dies.
>
> http://www.amazon.com/gp/product/B00KNC6E4G/ref=oh_aui_detailpage_o01_
> s00?ie=UTF8&psc=1
>
>
> Gary J
> N5BAA
>
> -----Original Message----- From: Bill Turner
> Sent: Sunday, November 16, 2014 8:55 PM
> To: Towertalk
> Subject: [TowerTalk] Some advice about crimp ;type coax connectors
>
> I haven't seen this discussed before so I thought I'd throw in my 2
> cents. Might help someone.
>
> I love crimp type coax connectors. Done right, they are faster and
> more reliable than solder type. I will never go back.
>
> First, there are two types of crimp connectors. They both are designed
> to have the braid crimped, but some of them are designed to have the
> center pin soldered. Do not mix up the two kinds. The solder type has
> a small cutout for the solder like PL-259's have had forever. The
> crimp type has a round pin with no cutout. DO NOT try to crimp the
> solder type and do not try to solder the crimp type. It won't hold.
> Don't ask how I know. :-)
>
> Always crimp or solder the pin first and then give it a good pull
> before you crimp the braid. It should not pull out, obviously. How
> much pull? I don't know exactly, but i think it should withstand at
> least ten pounds or so. More is better.
>
> In order to get a god crimp on the braid of the coax, all the braid
> wires must all be intact. In other words, if you nick a few strands
> and remove them, the crimp will not be as tight as it should be.
> Do it over.
>
> In order to get a really tight crimp, I like to put a single wrap of
> electrical tape over the braid first. The ferrule is not part of the
> electrical connection, so don't worry about that. it's only purpose it
> to press the braid tightly to the connector. The tape just enlarges
> the diameter and increases the pressure applied by the ferrule. You
> could instead use heat shrink tubing of the appropriate size.
>
> I highly recommend using a coax cutting tool, the kind that makes two
> cuts at once - one down to the center conductor and one down to the
> braid. It is well worth your time to get the depth of cur just right.
> These cutters are adjustable so practice on a piece of coax and figure
> wasting a foot or two until you have the cut perfect. You will be well
> rewarded in the long run.
>
> I learned all this the hard way. Hope this saves someone some grief.
> Comments welcome.
>
> 73, Bill W6WRT
> _______________________________________________
>
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73
Roger (K8RI)
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