Topband: Fsj4 series heliax around a rotor

[Carl]

>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