RST Engineering


Kit Electronics For Aviation and Communication


Aircraft Builder's Antenna Kit For Composite Airframes

RST-2802   $29







This kit includes a 25' roll of copper tape, a bag of 18 toroids, and the Antenna Reference Text  (click to download) on disk.  This amount of material is enough to construct 4 VHF & 2 UHF/GPS antennas.


Over the years we have written over 300 articles on all aspects of avionics design.  Several of them are directly concerned with the design of hidden antennas in composite aircraft.  We took the heart and soul of these articles and produced the Antenna Reference Text.  Everything we know about these composite aircraft 1 antennas is described in this Reference Text.

VHF NAV Antenna

RST Antennas Went Around The World On Voyager



The Story Of Our Composite Airplane Antennas


Back in 1978 the homebuilt airplane world was a'changin'.  Wood and metal were giving away to glass and foam.  Since fiberglass and resin are as transparent as air to radio waves, there was no reason to put drag-sticks outside the aircraft fuselage since they could be put easily and efficiently under the plastic skin.


You can buy composite aircraft antennas from the $5 that I charge up to hundreds of dollars for antennas with "magic properties" that are "hidden in epoxy" and "tuned to the airframe."  One of the companies that wants to sell you hundred dollar antennas pooh-poohs my "ferrite donuts" (toroids) as useless.


OK, here's the truth of it.  The toroids act as a very efficient "balun" that couples a BALanced dipole antenna to UNbalanced coaxial cable.  The little donuts simply keep reflected power from coming down the outside braid of the coax and upsetting the sensitive instruments near the coax. 


If you like, you can compare the toroids to the iron core noise filter on the alternator. In either case, the powdered iron toroids strip the noise from wires that can radiate interference to your aircraft radios and instruments.  It takes a very special blend of powdered ferrite material to do the job on a VHF antenna and it took us nearly a quarter of a year of experimentation to determine the exact blend that optimizes performance and eliminates noise. 


(Note 1 – some carbon fiber composite materials are not compatible with internal antennas.  Unfortunately, we cannot tell what carbon materials are usable with internal antennas and which are not.  The only way to really tell is when the cloth manufacturer releases the "ohms per square" of the material. Only then will we have a chance of determining which materials are compatible and which are not.  No other information is available right now.)

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Edition: 15 Jan 2020

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RST Engineering

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