[Elecraft] KPA100 SO-239 Help

[Jack Smith]

It's easy enough to inadvertently to rotate the center pin when mating 
with the PL-259 particularly with small diameter coax cable and where 
the connector is not the easiest to access. Push the center pin in, and 
then find  the coax isn't routed exactly like it should be, move the 
cable around and then push the shell into place.

This is more of an issue with adapters, BNC(F) to UHF(M) for example, 
where it isn't uncommon to rely upon the center pin to hold the adapter 
in place while getting the shell started. And some of the cheap imported 
adapters have poor shell threads to begin with which makes it more 
likely to spin the center pin.

Depending on how much slack is on the other end, it's possible to break 
the connection. I had a couple of special order amplifiers with these 
connectors that had exactly this failure mode. Wound up using flange 
mount UHF connectors to avoid the problem, although the single hole 
connectors are mechanically neater.

Mouser stocks a single hole UHF connector that doesn't have this 
problem, but it ships without a hex nut, lockwasher and ground tab 
washer. The hex nut costs more than the connector.

Jack K8ZOA

On 2/25/2011 1:47 PM, Mike Fatchett W0MU wrote:
> He is talking about prior to soldering.  I have seen these too.  So has
> HRO who had to send a bunch back for just this reason.
>
> On 2/25/2011 11:38 AM, Ron D'Eau Claire wrote:
>> An SO/PL239 is pushed on, not twisted, until the face of the male is against
>> the ridged edge of the female, then the outer shell is threaded on and
>> tightened. The center pin never turns nor has any torque applied.
>>
>> I cannot picture how you could "spin" the CENTER conductor. That would
>> require twisting the coax attached to the male half.
>>
>> Ron AC7AC
>>
>> -----Original Message-----
>> I've found the same problem with two batches of Teflon insulated, single
>> hole mount SO-239 connectors manufactured in China and purchased from RF
>> Connection. The center pin spins within the Teflon bushing and unless
>> the user is extremely careful when connecting a PL-259, the wire
>> connected to the center conductor will break off.
>>
>> I returned one batch and received a second batch that were supposed to
>> be correct and found the same problem. I rejected those as well.
>>
>> I agree that a connector with this problem should not be used - too
>> great a risk of damage to the internal wiring.
>>
>> Jack K8ZOA
>>
>> On 2/25/2011 12:58 PM, dw wrote:
>>> Hi John,
>>> If it were me, and there is a possibility that the inner wire soldered
>>> to the inner pin could freely spin around during the process of taking
>>> on/off coax at the back of the unit, I would not take the risk of
>>> compromising the inner wire such that it could twist, bird-cage or
>>> possibly short to gnd.
>>>
>>> N1BBR
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