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10-30-2013, 06:03 PM
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Join Date: Jul 2007
Location: Flower mound, tx
Posts: 69
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Transponder antenna fairing
With the addition of my ADSB antenna, I decided to dust off my fiberglass skills and clean up romeo yankee's belly. I bought the cheap antennas so it started looking like a forest under there. I highly doubt that any performance gains were made, but I had fun.
Early morning flight testing, work work work!
Last edited by DeltaRomeo : 10-31-2013 at 05:47 AM.
Reason: fixed pics
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10-31-2013, 09:24 AM
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Join Date: Dec 2011
Location: Kirkland, WA
Posts: 886
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Those look great!
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10-31-2013, 10:56 AM
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Join Date: Nov 2008
Location: Shreveport, LA
Posts: 1,002
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Will the fiberglass fairing diminish the effectiveness of the transponder antenna?
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10-31-2013, 11:23 AM
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Join Date: Dec 2011
Location: Kirkland, WA
Posts: 886
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I think fiberglass is radio transparent. This is why glass planes don't need external antennas.
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10-31-2013, 11:28 AM
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Join Date: Mar 2005
Location: Dallas area
Posts: 10,761
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Just don't make them out of carbon fiber!
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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10-31-2013, 11:47 AM
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Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,957
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Very nice! Can you please provide some detail on how these are attached? Do they attach to the aircraft or to the antenna, or both?
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Kurt W.
RV9A
FLYING!!!
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10-31-2013, 01:34 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Is there a TED antenna under the fairing?
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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10-31-2013, 03:24 PM
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Join Date: Jan 2006
Location: Green Bay, WI (GRB)
Posts: 476
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Contrary to what many believe a shark fin transponder antenna is not a rod and ball antenna covered with a aero foil shape.
Antennas are designed to operate at a certain frequency, in this case the transponder antenna is cut to length that is 1/4 wave length at 1030 to 1090 MHZ. This is called the electrical resonate frequency.
By covering the antenna with a insulating material or dielectric, the speed of the wave traveling on the antenna radiator slows down. No insulating or dielectric material is perfect in preventing electron flow and is expressed by the term dielectric constant. The effect on the speed of the wave is termed velocity factor.
With that said what does this mean to the average builder?
By covering the ball and rod transponder antenna with a fiberglass / micro cover (Dielectric material) the electrical resonate frequency is changed from its design frequency of 1030 to 1090 to a new frequency of 830 to 890 MHZ. The VSWR also increases to level that may exceed the transponder spec?s.
The only way to insure the modified antenna meets the transponder spec?s would be to plot the performance with antenna measuring equipment.
__________________
Don Pansier
Green Bay, WI (GRB)
RV-7 N450DP
W9LYX
Antennas for Experimental Aircraft
www.deltapopaviation.com
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10-31-2013, 03:46 PM
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Join Date: Dec 2011
Location: Kirkland, WA
Posts: 886
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I recently received DeltaPop's transponder antenna. It's rated at a VSWR of Less than 1.2:1 at 1030 to 1090 MHZ
Looks very nice dpansier. :-)
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10-31-2013, 07:42 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,514
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Hmmmmmmmm
This thread has been very helpful. I have two of the rod and ball antenna and was thinking bout a little aero treatment. Mainly just a trailing teardrop, but will be rethinking that.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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