Transponders

Overview
I stock a variety of transponders and transponder accessories as you can see in the table below. Further down this page is a transponder comparison table.

Transponder Overview Article
Eric Greenwell has written a very nice article which gives an overview of transponder terminology and available products. This article was originally published as two articles in Soaring magazine in February and March 2002,
and updated January, 2008 for publication on the Soaring Safety Foundation web site. Eric flies with a Becker transponder in his motorglider.
The article is available here: https://www.soaringsafety.org/accidentprev/articles.html.

Transponder Antenna Tips
DG has an excellent document on their web site with details on how to mount transponder antennas to gliders.
http://www.dg-flugzeugbau.de/Data/TN-DG/service-infos/2004-53-e.pdf

Antenna Cables
I offer transponder antenna cables made by Larry Goddard in several lengths. They include a TNC connector for connection to the transponder and a BNC connector for connection to a transponder antenna. They are available in 3 m (9.84 feet) and 5 m (16.4 feet) lengths.

Cable-Ant-LMR240-BNCm-TNCm

Transponder Antennas
Several transponder antenna options are listed on the Antennas page. The RAMI rod style and "shark fin" styles are the most popular. I recommend the shark fin style because I recall from my fluid dynamics courses that the two worst types of bodies in regard to drag are spheres and cylinders. For installations inside fiberglass, wood and fabric gliders, or in the vertical fin in carbon fiber gliders (with the fin made of fiberglass) you may want to consider the L2 antenna from AAE.

Aviation Transponder Interrogation Modes
Below is a link to a Wikipedia page which explains the difference between Mode A, C and S transponder interrogation modes and other interesting tidbits.
http://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes

Size Comparison
Below is a photo showing just how much smaller the TT21 is than a Becker ATC4401 transponder. The Becker transponder and ACK A-30.4 altitude encoder are on the left. The TT21 transponder and TC20 control unit are on the right. Click on the image to view a larger version.

Manufacturer Click on link to see details	Description	Photos Click on image to see details	Logo
ACK	Altitude Encoders
Advanced Aircraft Electronics, Inc.	Communication, Navigation and Transponder Antennas for use inside fiberglass, wood, and fabric aircraft, and in the vertical fin of carbon fiber aircraft with the fin made of fiberglass.
Becker	Mode C and Mode S Transponders
Comant	Antennas for transponders
(RAMI) R. A. Miller Industries, Inc.	Transponder Antennas
Trig	TT21 and TT22 Mode S Transponders with built-in altitude encoder and remote head