[TowerTalk] connectors

[K7GCO@aol.com]

In a message dated 7/29/00 10:34:24 PM Pacific Daylight Time, kb9mci@qsl.net 
writes:

<< 
 > > No more N connectors,  hi.
 
 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 an inch of sulfide (i have
 actually measured this amount!) on it but the inside will be nice and
 shiny.  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!)  Third, the connector is less noisy
 b/c 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.
 
 
 
 The way I put on the connector is close to the way the arrl handbook
 says to.  
 
 1.  first use a caliper to measure the amount of outer jacket to remove.
 2.  then cut the outer jacket with a hot dull knife.  no scored braid!
 3.  then fold back the braid and comb it out with a Stainless steal
 brush.
 4.  again measure the center insulator with the caliper and cut it with
 the hot knife.
 5.  fold the braid up now and slip the clamp over the braid.
 6.  fold the braid back and comb it with the s.s. brush again.
 7.  cut the braid to the proper length with shears not nippers!
 8.  solder the center pin to the center conductor.  
 9.  slide the connector body on and tighten the nut.
 
 Sure, it does take longer than a PL-259 but 10 minutes of time is just a
 small price to pay for a connector that will stand up to the elements
 for years.  
 
 Also make sure you use AMP connectors and get them from a reputable
 source if possible.  (I know some times you find a guy at a hamfest with
 in the bag amp connectors for 25 cents a piece)
 
 73's
 
 Bryan, KB9MCI
  >>
The type N connector has its merits.  However I had the problem where in cold 
weather the center soild condutor of RG-14 contracted so much it disconnected 
from the female socket.  It was flush at one time.  So this brings up the 
fact that any extra shrinkage of the center wire tends to pull the center pin 
out leaving only the small 4 finger pressing on the very small diameter pin.  
Unless the center pin is pushed with some compression against the female 
where it can make a larger diameter ring of contact, I feel the power 
capability is seriously reduced.  There is a very small impedance bump also

Further the compression of the rubber gasket on the ring that presses the 
shield for its connection expands slightly toward the shield and dielectric.  
The dialectric gives in-inparticular the foam coax.  This reduces the 
pressure on the shield and may explain some noisy connectors.  This allows 
the potential of moisture entry.  I've heard of moisture entering the open 
end past the rubber gasket.  So I recommend sealing and tapping the rear and 
then taping the ring.  This is a good joint then for less than 1KW.  Always 
run a high power heat test for progressively longer periods and check for 
heat on the center pin.  Be prepared for some surprises.

I have seen some high power dummy loads of Birds that use Type N connectors 
which I questioned.  I have access to one and will test it for longer periods 
at say 80 degrees and pass the info on to them.  I've seen some commercial 
high power rigs with Type N connectors.  The PL-259 center pin and shield 
still makes the best connection.  It's necessary at times to retention the 
female fingers in from time to time and clean the insides.  I use the acrylic 
spray around the center dielectric and then RTV silicone rubber and tape the 
rear.  I've never had water get in the coax although it can get inside the 
connector and may cause a problem. So it's a good idea to tape the whole 
connector.   k7gco

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