[TowerTalk] LMR 400 VS 9913?

[Roger D. Johnson]

Hi Bill...a big problem with 9913 and other air
dielectric lines is moisture
intrusion. The commercials get around this by
keeping their lines pressurized.
here's the scenario. The coax warms up in the
daytime sun, pressure builds
up and a small amount of air escapes. (PL-259's
are not gas tight!). At night,
the reverse happens and a bit of moist outside air
gets sucked in. Over a period
of time this moisture builds up and you wind up
pouring water out the end of
your coax. Connectors available for air dielectric
coax, such as Heliax, have
a gas port built in for connection of a dehydrator
or pressurized gas system.
I don't know what is available for 9913. If no
suitable connector is available,
I think I would bring the 9913 inside, drill a
small weep hole just before the
flex coax jumper, and put the whole thing in a
plastic box filled with silica gel
or some such moisture absorbent. Hopefully, the
air being drawn back in would
be dehumidified by passing through the absorbent.

GL and 73, Roger



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