R: [TowerTalk] connectors

[Maurizio Panicara]

If true that the coax braid of N connector is not soldered but pressed, the
whole cable is also made unmovable by the rubber squeezed material and
pulling the cable with several kilogram force does not produce any direct
stress on the shield.
When no moist or water penetrate the connector, the contact resistance of
braid to connector is and remains extremely low, surely better than inherent
solder conductivity (that already would exceeds needs).
Also the male-female junction (betwen two N connectors) is watherproof and
there is no change in the that contact resistance, of both inners and
shields.

The PL259 is not weatherproof inside (coax side) and between male and female
joints, shield contact is made by a screw tighening that's mostly
reliability zero (metal contracts and dilatate with cold and warm), shield
braid is soldered but there's no mechanical provision and cable might rotate
or slip eventually damaging braid wires, in case of cable pulling nothing
else than braid keeps force, the excess of tin on the edge of inner pin can
spread the blades of the female receptacle worsening the contact.

All considered, I can agree the N connector is not best for CONTINUOUS power
exceeding one Kw at VHF/UHF, definitely, this limit doesn't apply below 30
Mhz, at least up to amateur US legal power.
PL259 works, but is far from beeing a better connector than N under any
perspective, surely its not a good solution in case the power is higher than
normal and should suggest the use of  hardlines and better connectors like
7/16 or 7/8 flange (or bigger ones).

PL259 advantage is mainly because of a low cost and immediate approach in
mounting, the higher cost and the people "fobia" in spending 15 minutes to
finally learn the N connector mounting procedure are its disadvantage.

73,
Mauri I4JMY




----- Original Message -----
From: Tom Rauch <w8ji@contesting.com>
To: <towertalk@contesting.com>; Bryan Fields <kb9mci@qsl.net>
Sent: Sunday, July 30, 2000 1:44 PM
Subject: Re: [TowerTalk] connectors


>
> > I think that a N is THE BEST connector to use. The two gaskets give it
> > water resistance that no PL-259 can match.  After years of being outside
> > unprotected the silver may have .006 of a inch of sulfide (i have
actually
> > mesured this amount!) on it but the inside will be nice and shiny.
>
> It is more water resistant.
>
> > Secondly you do not need to heat the whole connector like you have to do
> > with a pl-259, this means no melted coax and no impedance bumps b/c of
> > melted dielectric. (i can never put a pl-259 on right the first time,
the
> > coax always melts!)
>
> That's a non-problem if you solder with a big enough iron and pre-
> tin, and if you use a good connector.
>
> On the other hand, the N depends on grabbing the braid with only a
> mechanical connection to prevent pulling out. The gaskets "sort-of"
> squeeze the jacket, but have no holding power.
>
> If the cable has a loose braid, or a flexible jacket, the center pin of
> the N will move all around when you pull on the cable.
> Mechanically, they are poor connectors for gripping the cable
> although they hold all right with thick braid hard jacket cables.
>
> My biggest gripe is they are low power connectors. They have the
> same approximate pin size and air gap as a BNC connector. Not
> exactly high-power construction.
>
> The SWR bump in a PL-259-SO-239 pair is in the 1/2 inch of area
> in the SO-239, where the impedance is about 35 ohms or so. 1/2
> inch of such a small bump causes almost no change in the system
>  below a few hundred MHz.
>
>
> >Third, the connector is less noisy b/c the the
> > center pin is under pressure from the connector.  This is very important
> > in repeater installations, especially in the duplexer. Many a crackling
> > noise has been traced to a bad uhf connector on a duplexer.
>
> At one time I was responsible for about 30 VHF repeaters. I never
> saw that problem even one time. Factually, the UHF connector
> makes a much better connection than the type "N". Both surface
> area and pressure are higher in the UHF connector.
>
> Now I don't object to "N"s where they are needed, like on SWR
> critical upper VHF and UHF systems where power levels are low.
> But when I get hardline with N fittings I machine them into good old
> UHF style fittings by boring out the center hole and shortening the
> threaded area a bit. I then gut a SO-239 and use a brass tube to
> solder the center pin to the feedline.
>
> None of those hard-to-assemble easy-to-pull-apart low-power N
> connectors in this fellows station!
>
>
> 73, Tom W8JI
> w8ji@contesting.com



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