Hmmm... The REAL problem is the flexible coax run past the point where the
rotating mast joins the non-rotating support structure...
Generally, that little bit of an "S" bend in the cable at that
connection point is more than sufficient to deal with any thermal
expansion/contraction stress at that point, provided your cable is
properly fixed to the antenna boom. Oddly enough good old fashioned
vinyl electrical tape is the best material to use for this purpose.
Properly wrapped and layered, it will hold the coax to the boom with
strength equal to the cable and may last longer than the cable or the
antenna for that matter! Plastic zipties tend to kink or dent the cable
if drawn up too tightly, and most are sensitive to ultraviolet rays from
the Sun, (even some of the "black" ones) and they will break over time
unless protected from sunlight (with the same black electrical tape that
would hold the cable just fine on its own:-)
My rover installations have experienced more problems with trees damaging
antenna elements and the occasional loosening of antenna hardware, or in
some cases the outright failure of antenna support hardware...
In the one case where the rotator came apart and all the rover antennae
went over the back of the vehicle at 60 MPH, the cables taped to the booms
kept the whole mess more or less together!
Eric
KB7DQH
> What is the engineering reason that you need a strain relief loop even
> though the coax is supported and there is no pull on the connector?
>
> I have a dozen antennas arranged just as you describe, no problems so far
> after six years.
>
> Jim, AF6O
>
>> Of course, taping the coax to the boom supports the coax so there is no
>> pull
>> on the connector. But the engineer in me says I should place a strain
>> relief loop at the connector.
>> Michael - N6MEF
>
>
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