[TowerTalk] Crimp on Coax connectors

[wc1m73 at gmail.com]

You have to solder the center pin if it's not designed to be crimped, as is the case with LMR-400 compatible UHF crimp connectors like the ones from DXE. I believe the reason the center conductor is solder-only is because the center conductor of LMR-400 type cables is too thick relative the standard diameter of the UHF center pin to fit in a swaged crimp section.
 
But you're right that it's bad if the solder wicks down a stranded center conductor. For that reason, I only solder 1/8" or so of the center conductor to the end of the tube. I think this is safe because the center conductor doesn't flex inside the tube. However, I've been tinning stranded center conductors to make it easier to prevent them from unraveling as they get pushed in the tube, which can happen with large stranded center conductors like LMR-400. This is likely setting up the situation you describe, so I'm going to try not tinning the center conductor next time.  

73, Dick WC1M

-----Original Message-----
From: Richard (Rick) Karlquist <richard at karlquist.com> 
Sent: Friday, September 6, 2019 12:28 PM
To: W3YY <w3yy at cox.net>; towertalk at contesting.com
Subject: Re: [TowerTalk] Crimp on Coax connectors

I'm surprised no one mentioned the well known reason not to solder:  the solder wicks up into the stranded center conductor and stiffens it which risks failure if there is a lot of flexing.
It will break right where the wicked solder ends.
This is why you will never find a solder joint in airplane wiring.

It might be OK for a solid center conductor though.

Rick N6RK