Metallic paint and composite antenna signal strength

On larger aircraft, there are very few antennas the manufacturer will
let you paint. You can get by with metalics on some such as the
comms, but not any of the L-band, TCAS, or other high frequency ones.
As a rule though, we won't cover the antenna manufacturer's paint with
anything else.

I recently had a new Gulfstream that the tail radome that covers the
satcom, Direct TV, and high-speed data antennas that had to be changed
because the paint was too thick and attenuated the TV and data
signals. The satcom worked fine.

Experience has shown me that with other than small metallic stripes on
the nose radome, they won't pass a transmissivity test on the range
and have to be stripped and re-painted. The white urethane base coats
don't cause a problem there.

"Don Hammer" wrote in message
news:1119738126.4b52018cd82f8bdc4b584a58e183d17a@t eranews...

On larger aircraft, there are very few antennas the manufacturer will
let you paint.

A holdover from the days when most paints had colors with pigments starting
with "lead", "cadmium", "copper" and the other heavy metals. With the EPA
ban on truly metal based paints as the pigment, why should the manufacturer
go back and redo the whole damned testing procedure with the new oxide based
colors.

Besides, at these speeds, there are some legitimate static buildups that
come in to play to require "furry paint". At Mach .25, these effects are
hardly noticeable.


You can get by with metalics on some such as the
comms, but not any of the L-band, TCAS, or other high frequency ones.
As a rule though, we won't cover the antenna manufacturer's paint with
anything else.

I don't have a problem with that. If you don't have an antenna pattern
range on which to "prove" your work, the best course is to avoid paint.
However, we were talking about an experimental here, and THIS is where we
prove the new concepts that eventually work their way into production
aircraft. How many production aircraft had Whitcomb winglets installed
until several thousand EZs proved the point?



I recently had a new Gulfstream that the tail radome that covers the
satcom, Direct TV, and high-speed data antennas that had to be changed
because the paint was too thick and attenuated the TV and data
signals. The satcom worked fine.

No problem. If I was working with submicrovolt signals, my advice would be
to save every tenth of a dB possible. Here we are talking noise margins of
forty to sixty dB and the dB or so that thin, thick, or semimetallic paint
would introduce is a second order effect at best.



Experience has shown me that with other than small metallic stripes on
the nose radome, they won't pass a transmissivity test on the range
and have to be stripped and re-painted. The white urethane base coats
don't cause a problem there.


And we both know that the "small metallic stripes" are there to conduct
lightning strikes from the epoxy to the metal airframe. Ever seen a radome
that takes a REAL lightning pop that goes through the epoxy before it gets
to the metal stripes? The sucker looks like it had a huge popcorn kernel
under the skin.

Jim

And we both know that the "small metallic stripes" are there to conduct
lightning strikes from the epoxy to the metal airframe. Ever seen a radome
that takes a REAL lightning pop that goes through the epoxy before it gets
to the metal stripes? The sucker looks like it had a huge popcorn kernel
under the skin.

Jim


All good points Jim.

Larger aircraft radomes have lightning deverter strips installed on
the outside of the glass. What I'm talking about is metalic paint
trim stripes. We try and keep all metallics off of the radomes
because it will attenuate the signal if it is anyway near the signal
path. The radome on the tail also has diverters. Their placement is
engineered to be out of the way of the signal.

Don