Another good point about the use wire ties (zip ties) . Tape is the best and
use the 3M stuff that cost about $3.60 a roll. Do not use the bargain
tape for this application.
I made the mistake of using the white wire ties on a 2m H frame back in the
70's and was up there later at 100 feet with two poles trying to tape the
coax back to the frame and booms. The black ones are UV resistant but
pulling them tight will cause a bump in the coax impedance especially on the
softer cables.
Ron
On Sat, Mar 21, 2009 at 7:45 PM, <kb7dqh@donobi.net> wrote:
> 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
> >
> >
> > _______________________________________________
> > VHFcontesting mailing list
> > VHFcontesting@contesting.com
> > http://lists.contesting.com/mailman/listinfo/vhfcontesting
> >
>
>
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting@contesting.com
> http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|