I have used Andrew FSJ4 cables for years as rotor loops. Andrew does not
recommend it outdoors, but I have come up with a good technique for its
use. When you put the connectors on each end, be sure to remove about 1/2”
or more of the outer plastic sheath behind the connector body so the copper
is exposed. Then knead some butyl rubber sealing goop in there to provide a
strong vapor barrier just behind the connector body. Cover that with some
wraps of good vinyl tape. Superflex is very prone to getting nicks in the
outer jacket and allowing water to get in under the jacket. This has
migrated to inside the connectors many times for me, causing no end of
trouble on 1296 and 2304 MHz. (One drop of water will kill 2304 signals by
30-40 dB...hard to believe!) I think the water pressure can build up and
the hydrostatic head is enough to push through the simple O ring inside the
connector.
Since employing this technique, my water entry problems have largely
disappeared with Superflex. I have yet to have a cable break with flexing.
All my failures were water related. I cover each connector with a layer
or two of good tape, then use butyl rubber and follow that with more tape
and some wx seal like Scotch kote or some form of oil based varnish to
make sure there are no air pockets open where water can enter.
73
Dave K1WHS
Thanks for that info Dave and I can see where the FSJ may offer a slight
edge heading into the microwaves over LMR-400UF.
But assuming a rotor loop of 5' the difference at 432 is a whopping .04dB
and I would think that the loop would be a bit longer or even double as in 2
turns for the FSJ. Suddenly there is either no difference or even a loss for
the FSJ. The original poster was planning to make the complete run from the
FSJ for protection from critters and no frequency was mentioned; but at HF
to low UHF there is no loss benefit worth mentioning for a rotator loop.
Maybe for a CB operator or a ham running tubes with handles the extra power
handling might be important.
I'll stick to the LMR-400UF, cable cost and connectors are reasonable, and
there is no danger of copper breakage and water ingress
Carl
KM1H
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