[TowerTalk] Connectors

[i4jmy@iol.it]

Hi Chris,

You don't frequently find N connectors on amateur transceivers, 
amplifiers and antennas because they are expensiver than UHF type and 
mainly because a large number of HAMs doesn't want to learn how to 
install them. Knowing this situation, it would be a double mistake to 
use N connectors, at least from the manufacturer perspective.
Most of professional equipment stopped with UHF during the late 70' and 
you can find HF transmitters antennas and amplifiers with N connector 
rated for RF power well exceeding the Kilowatt.
The bigger size of the UHF central pin connector lead to believe that a 
UHF connector withstand more current than N but this is true only at DC 
or in the lowest HAM band where mechanical precision is a less 
stringent matter.
Not counting that even a small tin excess in the edge of an UHF central 
pin of male often causes to open the fingers of UHF inner receptacle 
thus further reducing quality and quantity of the contact.
Another gap with UHF is that outer parts of male and female should be 
perfectly planar and pressed to insure a good contact(as it is in EIA 
connectors) meanwhile the typical rough construction and expecially the 
screwing of the outside ring of UHF doesn't insure it. The outer ring 
often looses, expecially outside where hot and cold themperature cause 
a number of thermal cycles most days of the year. It's just proper to 
point out that optimal weatherproofing an UHF connector that inherently 
is not, doesn't prevent outer ring losening because of thermal cycles.
Another weak point with UHF is that cable is not pressed inside 
connector and if through shield or even the inner some umidity migrates 
because of capillarity effect, also passes into connector and contacts.
It's not uncommon to remove a self amalgamating tape from an UHF 
connectors joint, finding out a perfect bright outer surface and then 
to discover oxidization inside.
Concerning N power rating, the connector it's perfectly useable at 
800/1000 W with any reasonable SWR at 150 MHz and above.
Using FM broadcast equipment I personally made a test using N 
connectors and 6 KW at 100 MHz on a dummy load. After 20 minutes the 
connector was quite warm but much colder than the teflon cable used and 
there was no failure or irreversible damages.
It's evident that reducing the forward power to 1.5 Kw and the 
frequency below 30 MHz there is no kind of problem with RF currents, 
direct or reflected and using N connectors and problems of other nature 
are also avoided.

73,
Mauri I4JMY
   
  



> ---------- Initial message -----------
> 
> From    : owner-towertalk@contesting.com
> To      : <towertalk@contesting.com>
> Cc      : 
> Date    : Mon, 2 Apr 2001 10:30:31 +0200
> Subject : [TowerTalk] Connectors
> 
> After many years of struggling with soldering into little holes on 
lousy
> connectors, I gradually started migrating to N connectors.  They are 
less
> lossy, generally waterproof and mate more reliably than UHF 
connectors.
> Unfortunately, ham equipment suppliers continue to churn out high-
power
> equipment with UHF connectors, for reasons that I cannot understand.
> 
> However, the reason for this message:  I recently (a year ago) took 
the
> plunge and invested in a crimping tool.  I should have done it two 
decades
> ago!  The connectors take a lot less time, are more reliable and look
> better.  I can generally install a UHF or N connector, male or 
female, in
> under four minutes on RG213-type cable; even when dangling from the 
tower.
> 
> The connectors are priced similarly to solder-on types and are freely
> available from professional communications sources in this country.  
I can
> only imagine they must be similarly easy to find in Merica.
> 
> If you really insist on soldering connectors, you absolutely must 
invest in
> a Portasol butane-powered soldering iron.  It produces about 175 W of 
heat,
> enough to solder any connector (at least ones that amateurs would 
use).  I
> have not found another torch in the same league.  It is sufficiently
> powerful to heat the casing if required, so that you can get good 
flow and
> good mating with the braid.
> 
> 
> Chris R. Burger
> ZS6EZ
> 
> 
>