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To: lml
Date: Tue, 25 Jul 2006 11:14:05 -0400
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From: "Charles R. Patton" <charles.r.patton@ieee.org>
Subject: Re: [LML] ELT antenna
In-reply-to: <list-1314636@logan.com>
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I had the same thoughts and had the occasion to measure a IVP under 
construction and as I recall the value was about 5 ohms which makes it 
to be about 5 ohms/square.  So against a nominal 50 ohms at the feed 
point, maybe 10% loss, which is not the worst thing in the world.    
Therefore I would essentially think of carbon composite sheets as metal 
sheets and design accordingly.  I.e., if the antenna is inside a carbon 
shell, it won't work well, if outside it will, the same as in a 
traditional aluminum construction.  Because of windows, cracks (seams at 
the door), etc., there is leakage from the inside of a aluminum plane, 
but it will be very directional and likely to be very poor for ground 
communication signals.  My two cents worth.  (A further sidebar.  Since 
carbon fiber it is a measurable 5 ohms, it will not shield as well as 
aluminum, therefore there will be significant leakage in comparison to 
aluminum   I.e. up close it might appear that you can transmit/receive 
from antennas inside, but I would estimate that the attenuation is on 
the order of 20 dB or more.)
Charles Patton


Paul Lipps wrote:
> Jim Cameron,
>     Putting the antenna on the outside of a carbon plane is almost as 
> bad as putting it on the inside. Being a carbon conductor (think 
> resistor), it will absorb most of the power put into the antenna, 
> especially if its impedance appears similar to free-space impedance.