Black paint often uses carbon black as a pigment. Carbon black, being
conductive, makes a fine absorber, although, depending on density and
thickness it may or may not have a significant effect. Likewise, white
paint usually uses Titanium Dioxide as a pigment (so do most other
reasonably bright colored paints, TiO2 is also added to improve "covering
power") TiO2 has a fairly high dielectric constant, and so, can alter the EM
properties of objects it covers (like covering in plastic, except worse).
Ideally, one designs the radome so that these effects are minimized, either
by careful selection of materials, or by careful design (for instance,
honeycombs that are 1/4 wavelength thick).
Jim, W6RMK
----- Original Message -----
From: "Dick" <rbodine@cpinternet.com>
To: <towertalk@contesting.com>
Sent: Sunday, April 13, 2003 3:25 PM
Subject: Re: [TowerTalk] Painting fiberglass antennas
> Quite a few years ago we decided to dress up our jets with new paint
> jobs and the radome was included. Nice, black, and glossy, the radome
> looked real nice against the new paint job. Then we started getting
> complaints from the aircrews that the radar wasn't getting distant
> contacts like it used to. We checked the receivers of the jets that
> were being written up but found they were were seeing as well as they
> ever did. For the nuts of it we did a radome off /on test and found the
> source of the problem.... it was the paint that was attenuating the
> signal and by several db. We had the paint stripped and confirmed that
> was the source of the problem. The paint was a good quality paint, it
> had to be to stay on the nose as well as it did. As I recall, the paint
> shop contacted the depot and found out what was recommended and obtained
> the correct stuff. Now I know paint has come a long way since those
> days and the frequency was considerably higher but it makes me still
> question if painting the fiberglass is a good idea unless you know for
> sure the paint won't cause some attenuation.
>
> Open for comments... 73
> Dick, N0IM
>
> --
> Dick Bodine
> mailto:rbodine@cpinternet.com
>
>
>
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>
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