[TowerTalk] connectors

[Tom Rauch]

> 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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