Carbon fiber vs. antennas

Yes, I got results on the carbon fiber and I would have SWORN that I posted them
to this site.

Putting a GPS antenna UNDER a small bowl-shaped carbon fiber radome immediately
killed any GPS signal into a 27 dB gain active antenna INCLUDING satellites that
were directly overhead.

Figuring that the carbon was so lousy a transmissive path, I drilled a hole on
the top of the bowl and used the bowl as the groundplane. VIOLA. The GPS
antenna worked every bit as well on TOP of the carbon fiber as it did on a metal
ground plane of approximately the same size.

I can't say this is true for any other service than GPS (transponder, vhf nav &
com, etc.) but it did test well for GPS.

Jim



Richard Riley
shared these priceless pearls of wisdom:

-
-Did you ever get results on the carbon?

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Jim, if I install a transponder pin with a carbon fiber ground plane,
inside a fiberglass fuselage, what equipment is needed to see how well
it's working? Or do I just fly around and ask ATC "Can you see me
now? Can you see me now?"

(actually, I've already installed it, but I'm not flying yet.)


On Wed, 31 Dec 2003 15:57:13 -0800, Jim Weir wrote:

:Yes, I got results on the carbon fiber and I would have SWORN that I posted them
:to this site.
:
:Putting a GPS antenna UNDER a small bowl-shaped carbon fiber radome immediately
:killed any GPS signal into a 27 dB gain active antenna INCLUDING satellites that
:were directly overhead.
:
:Figuring that the carbon was so lousy a transmissive path, I drilled a hole on
:the top of the bowl and used the bowl as the groundplane. VIOLA. The GPS
:antenna worked every bit as well on TOP of the carbon fiber as it did on a metal
:ground plane of approximately the same size.
:
:I can't say this is true for any other service than GPS (transponder, vhf nav &
:com, etc.) but it did test well for GPS.
:
:Jim
:
:
:
:Richard Riley
:shared these priceless pearls of wisdom:
:
:-
:-Did you ever get results on the carbon?
:
:Jim Weir (A&P/IA, CFI, & other good alphabet soup)
:VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
:http://www.rst-engr.com

On 31-Dec-2003, Jim Weir wrote:

Putting a GPS antenna UNDER a small bowl-shaped carbon fiber radome
immediately
killed any GPS signal into a 27 dB gain active antenna INCLUDING
satellites that
were directly overhead.


Yes, carbon fiber is an excellent RF absorber, particularly at GPS
frequencies.

--
-Elliott Drucker

Date: 1/1/2004 1:04 PM Central Standard Time
Message-id:


On 31-Dec-2003, Jim Weir wrote:

Putting a GPS antenna UNDER a small bowl-shaped carbon fiber radome
immediately
killed any GPS signal into a 27 dB gain active antenna INCLUDING
satellites that
were directly overhead.


Yes, carbon fiber is an excellent RF absorber, particularly at GPS
frequencies.

--
-Elliott Drucker


How about at radar frequencies? Does this mean a carbon aircraft are less
visible to radar?

Dan, U. S. Air Force, retired

Had you noticed that the "stealth" aircraft were mostly black? Like as in made
out of carbon fibre?

Jim



-How about at radar frequencies? Does this mean a carbon aircraft are less
-visible to radar?
-
-Dan, U. S. Air Force, retired

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Would you mind keeping your gratuitous comments on the obvious to yourself?

Jim



shared these priceless pearls of wisdom:

-Yes, carbon fiber is an excellent RF absorber, particularly at GPS
-frequencies.

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

In article ,
(B2431) wrote:


Date: 1/1/2004 1:04 PM Central Standard Time
Message-id:


On 31-Dec-2003, Jim Weir wrote:

Putting a GPS antenna UNDER a small bowl-shaped carbon fiber radome
immediately
killed any GPS signal into a 27 dB gain active antenna INCLUDING
satellites that
were directly overhead.


Yes, carbon fiber is an excellent RF absorber, particularly at GPS
frequencies.

--
-Elliott Drucker


How about at radar frequencies? Does this mean a carbon aircraft are less
visible to radar?

Dan, U. S. Air Force, retired

Nope -- carbon fiber is a conductor and behaves similarly to metal --
especially if you have parts of .25 wavelength. Remember -- Edison's
first light bulbs had graphite filaments.

Do not let carbon parts touch aluminum, as the aluminum will corrode
from electrolytic action. A carbon fiber plane will act as a ground
plane for antennae, too -- as long as you have good electrical contact
with the fibers.

Orval Fairbairn
shared these priceless pearls of wisdom:

-Nope -- carbon fiber is a conductor and behaves similarly to metal --

Sorry, Orval, that just ain't so. I've done some preliminary work with carbon
fiber and at most frequencies below VHF it isn't a conductor and it isn't an
insulator. It is a great big resistor.


-especially if you have parts of .25 wavelength. Remember -- Edison's
-first light bulbs had graphite filaments.

Nope. Linen threads dipped in carbon black. Hardly graphite.


-
-Do not let carbon parts touch aluminum, as the aluminum will corrode
-from electrolytic action. A carbon fiber plane will act as a ground
-plane for antennae, too -- as long as you have good electrical contact
-with the fibers.

That isn't so. Please don't spread misinformation unless you've DONE the tests
and can publish your test results.

Jim



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Pardon?

Tom

"Jim Weir" wrote in message
...
Would you mind keeping your gratuitous comments on the obvious to
yourself?

Jim



shared these priceless pearls of wisdom:

-Yes, carbon fiber is an excellent RF absorber, particularly at GPS
-frequencies.

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com