[TowerTalk] PL-259 RF Coaxical Connectors

[K9MA]

I recall from my space hardware days that all the connector pins were 
crimped. The crimp tools had to be regularly calibrated, and 
periodically a pull test performed.

Crimped connections can be very reliable, but they have to be done right.

73,
Scott K9MA

On 2/16/2021 4:53 PM, Lux, Jim wrote:
> On 2/16/21 2:05 PM, Rob Atkinson wrote:
>>> I do not use solderless crimp on PL-259 connectors.  PL-259 
>>> connectors were
>>> designed to be soldered!
>> Starting a few years ago I experienced an intermittent and sudden loss
>> of signal into one or two of my receivers.  Sometimes I'd be tuned to
>> a vacant frequency and have band noise and hiss in the background.
>> Then it would suddenly vanish.  A few times I thought a strong
>> unmodulated carrier had come on frequency but it turned out to be a
>> sudden drop in RF level of 10 or 20 dB.  I could pot up the RF gain
>> and get signal back and I began by suspecting some sort of bad relay
>> connection somewhere or a loose screw on a rear panel.  Because it was
>> intermittent, it was tough to find and the problem plagued me off and
>> on.  You all have been there before:  One day I just happened to <fill
>> in the blank> and eureka -- in my case it was a jumper at a coax
>> switch I happened to nudge and strong band noise returned.  Well
>> hello, what's this?
>>
>> It turned out to be a jumper made with crimp connectors.  You can love
>> them all you want but here's what happens--after a few years the crimp
>> - braid contact wears out.  It ceases to make good low resistance
>> continuity for the extremely weak RF currents flowing.  Maybe it's
>> mechanical failure; maybe it's chemical -- whatever it is, _braid_
>> does not hold up in a crimp long term.  Compression connectors with
>> Heliax or other hard line with a solid compressible copper shield are
>> a different story.  But in my opinion, any coaxial line using braid
>> for the outer conductor must be soldered to its connector.
>
>
> On the other hand, there *are* crimp connections on stranded that are 
> more rugged than solder. I suspect it's a matter of connector design 
> and proper tooling.  Cable TV uses almost exclusively crimp connectors 
> on a foil/braid and they have decent performance over the years.
>
> I'd have to go look what we do for spacecraft, but in general, we 
> prefer crimped over soldered.
>
>
> it's NASA STD 8739.4 - and Appendix B is about coaxial cable 
> problems.  The concern seems to be if the clamping system clamps the 
> jacket, then the jacket will cold flow.
>
> I don't know that there's a lot of practical difference between a 
> "wrench tightened" N connector that clamps the braid and a crimp 
> (assuming the crimp is properly done) - Amphenol 172102-2 is a crimp N
>
>
>
>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk


-- 
Scott  K9MA

k9ma at sdellington.us