nuckolls.bob(at)aeroelect
Guest
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 Posted: Sun Jun 06, 2010 10:36 am Post subject: PolyFiber silver coats and their effect on radio signals |
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At 12:55 PM 6/6/2010, you wrote:
| Quote: | So all those decals on FAA-PMA GPS and transponder antenna radomes
saying "Antenna: Do Not Paint" are flooby-dust, as I long
suspected... good to know.
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Not too fast . . . while the effects of the suspended conductive
material has only a small effect on the intensity of passage/
reflection of a signal at radio frequencies, the effect is not ZERO.
In terms of first order effects, it might even be exceedingly
difficult to measure. However, there are also BENDING or LENS
effects to consider.
Radar transmits energy in the hundreds to thousands of watts
while expecting to see very tiny reflections of that energy from
far objects. Further, the DIRECTION from which those signals
are perceived to come is important in deducing the location
of radar-painted object.
Even pure insulators will bend the direction of a radio
frequency wave front not unlike the manner in which a prism bends
light as a function of its frequency (color). While painting
a radome may have little effect on the strength of a
passing signal, it can have a profound effect on changing
the direction of the wavefront. I would think that coatings
carrying conductive particulates would be even worse.
I can tell you that it's an exceedingly difficult task
to craft an "optically perfect" radome that's also friendly
to airflow over the nose of an aircraft. The act of painting
an otherwise optimized radome could have an effect on quality
of the targets display not unlike viewing an object through
a glass brick.
But yes, for non-directional interpretation of received
energy like GPS, Transponders, etc. the effects of additional
paint are very tiny indeed.
Bob . . .
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