Topband: Fsj4 series heliax around a rotor

[Dave Olean]

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