[Elecraft] SO-239 Concerns -- Another Perspective

[Tom W8JI]

> 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.

Nearly all problems I've seen with female contact flaring were caused by 
males that have solder on the outside of the pin, increasing pin diameter. 
I've seen a few really cheap females, too.

I've got many dozens of connectors in my system, and N's are just as much or 
more problem overall. So are BNC's, especially when subjected to high 
humidity.

The only nearly perfect connectors are DIN, type-C, or EIA flange 
connectors.

> Note that a type N, C or BNC pair makes it's shield connection through the
> inner spring tension sleeve, maintaining contact almost until the pair
> separates. The backshell is just used for mechanical, not electrical,
> purposes.

Actually the shell provides a backup for continuity in the N, and while I 
have fewer shell tightness problems I have a whole lot more center pin 
issues or pin arc-outs from lightning or wrong antenna selection.

The thing I like best about type N's is I can chuck them up in my lathe, cut 
the female a little on the end, bore out the center, press the guts from a 
Teflon SO-239/PL259 in the middle, and convert them to UHF type connectors. 
I convert all my surplus heliax connectors to UHF style. :-)

I avoid shell tightness problems by LIGHTLY using pliers, and snugging, 
backing off, and resnugging two or three times. That way I make sure the 
locating bump on the male is in the female notch and everything is flat, and 
there is some distortion on the shell to keep it locked. Anyone who works on 
cars understands that something has to slightly stretch or distort to lock a 
threaded connection. Finger tight or wrist tight will never hold under 
temperature or vibration, but a slight snug with piers will.

I probably have a few hundred connectors in the system. I can't recall the 
last time I had a tightness or water issue with a UHF, although I sure have 
had pin problems in N's. Mostly due to someone picking the wrong antenna at 
full power....or lightning. Most of the N's left in my system are being 
replaced as they fail.

73 Tom