[Elecraft] SO-239 Concerns -- Another Perspective

[Paul Christensen]

> 1. Many SO-239s provided as part of radio equipment are not up to the
> quality of Amphenol units. In particular, the spring fingers of the socket
> for the male pin loosen over time to the point that the connection becomes
> less than solid. This is particularly a problem if the connector is used
> repeatedly. I usually replace with Amphenol units...

I have nothing against the SO-239s used in the K3, although during assembly, 
I decided to use Amphenol connectors as a substitute.  I also like using 
Amphenol-branded SO-239s on custom projects.  The added expense for the name 
is usually a small percentage of the total project cost.

> 2. The other potential problem with UHF connectors, in my opinion, is the
> integrity of the shield connectivity through the connected pair. If the
> backshell loosens, there is no longer a solid connection either at the
> toothed parallel portion, nor through the backshell.

And that's my objection to the UHF connector combination.  For example, I 
gained 0.75 dB in the shack on 10m simply by re-tightening a series of 
connectors that seemed hand-tight.  After installing some new equipment, I 
decided to conduct a loss budget analysis from the transceivers to the shack 
antenna output ports and all points in between.  I was seeing too much loss 
through the system.

When I used slip-joint pliers and ensured that the teeth of all '259s mated 
with the '239s, measured shack losses were minimized.  I have a lot of 
switching here and with switching, there are many UHF connectors. 
Electrically, the sole conduction mechanism of the PL-259 is the inner 
surface of the threaded shell and to Joel's point, the threaded shell is 
only press-fitted against the connector body.  A low-loss connection path is 
wholly dependant on the force of the shell to the body and the shell against 
the 239 threads.  It's a miracle the UHF connector works at all.

Paul, W9AC