Chuck,
That is true, but is ignoring the fact that the threads of the PL259 are
providing the only contact with the SO239. They must be solidly tight
for reliable conductivity to the shield of the coax. All contact from
the SO239 to the coax shield is by pressure contact. Finger tight may
"work", but unless one has very strong fingers, that is not tight enough
to assure a good connection.
A parallel is putting a locking nut on a screw by using a 2nd nut -
often done if you want to use the screw as an axle, like putting the
screw through a hinge (think a trailer rear gate). If you put the 2nd
nut on the screw with only finger pressure, it will likely back off with
slight vibration and twisting nullifying the locking effect. OTOH, if
you fasten the two nuts together with a slight twist of the wrenches,
the two nuts will not move and will remain locked together. It is not
the friction between the 2 nuts that does it, but there is a slight
elongation of the screw threads that keeps significant pressure on the
two nuts to keep them together.
The same principle applies to a PL-259 to SO-239 thread engagement.
We may have "gotten away" with only finger tight in the past, but is one
possible cause of failure.
73,
Don W3FPR
On 9/17/2018 5:05 PM, hawley, charles j jr wrote:
I've found that wiggling the body of the plug while tightening the threads
makes the pl259 quite tight with the pins firmly seated in the notches. The
motion allows the pins to find the deepest well of the notch.
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