At 09:42 PM 03/22/06, you wrote:
>At 3/22/2006 20:31, you wrote:
> >At 02:58 PM 03/22/06, you wrote:
> > >I have a shiny new Antennex FG1440 2 meter repeater antenna, and I
> > >thought that before we install it on the tower, maybe I should put an
> > >additional protective coating on over the fiberglass. Looking for
> > >something that would not get brittle and crack off any time soon. Any
> > >ideas? Urethane maybe? I once used some urethane designed as a
> > >marine finish with great results, but I'm open to suggestions..
> > >
> > >Thanks,
> > >dave na6df
> >
> >One local guy is using a double layer of white heat shrink. Went up
> >about 3-4 months ago. Dunno how it's going to stand up to to summer
> >sunlight / UV.
> >
> >The outside gelcoat is what gives fiberglass its watertight properties.
> >Too many antennas have "died" after the fiberglass allowed rain water
> >ingress.
> >
> >Be very careful that whatever you use is either clear or has a NON-
> >METALLIC pigment, for example, many white paints get the color
> >from titanium dioxide, a metal.
> >Black is OK as the color comes from lampblack(carbon) and won't
> >detune the antenna.
>
>FYI, carbon is a nice absorber. You may actually notice an improvement in
>VSWR, but the antenna performance may degrade dramatically. The hideous
>thing about that is unless you compare the antenna side-by-side with
>another antenna of known gain, measure it's gain on an antenna range or do
>a calorimetric measurement of the radome (heating under power), you may
>never know if you're installing a good antenna or a very leaky dummy load
>on your tower.
>
>I recently retuned/refurbished a 460 StationMaster by adding aluminum tape
>rings, coating with clear marine resin, & painting with a couple of coats
>of white Krylon. At each step I rechecked the VSWR to make sure what I was
>doing wasn't detuning the antenna, as I'd spent quite a bit of time
>optimizing the aluminum tape width & position. Neither the marine resin
>nor the white paint had any effect on VSWR or received signal strength.
>
>& yes I've been asked to write an article about the antenna mod. Been very
>busy with the LA Marathon & moving one of my repeaters that lost it's tower
>(tree) last year. Maybe I'll get to it next month if things calm
>down a bit...
>
>Bob NO6B
Yeah, in rereading that it could be misread - I meant it as carbon being
not metallic, not as in being a good coating.
Mike
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