Transponder + ADSB + ELT = 3 antennae. The Dynon transponder unit is "SV-Xpndr-261" and the antenna connection is a TNC male from the antenna locking onto TNC female on the back of the unit. The Dynon ADSB unit is "SV-ADSB472 and needs a BNC male connector locking onto the BNC Female on the back of the unit. The ELT unit is likely to be the Artex ELT 345 with a BNC male connector locking onto the BNC female on the back of the unit. Along the way to my antenna install I took a few detours and learned a bit. I bought and figured out how to use a vector network analyzer - it was a fun way to master a slick piece of test gear. After carefully making 2 high tech annular antennae, I decided to use the simpler "ball on a stick", and then I made and discarded 3 different kinds of ground planes. I then removed and discarded my homemades in favor of something small, pre-made and inexpensive listed on Amazon (found by Del Schier). See the attached Word file for pictures. As sent from the manufacturer, it worked well only on 1090 MHz and the newer all-in-one transponders seem to require an antenna that works on both 978 MHz and 1090. Del created a simple mod and now it works on both frequencies with < 1.2:1 VSWR. "...I simply soldered .65 mm brass extensions onto both sides of one of the pair of dipoles and it now resonates at both frequencies. See attached photo of the mod and the VSWR plot. Note: the little triangles on the plot are at 978 and 1090." In place of soldering onto the circuit board, I used copper foil with a conductive adhesive. Per Del: "It should have the same performance as a 1/4 wave rod or any BIG $$ dual frequency TSO'd antenna and it is very light and does not require a ground plane." As installed, I have SWR's of 1.2 (ADSB) and 1.3 (transponder). Rather than make cables with SMA connectors, I'll buy those online. Today's ELT's operate on both the old 121.5 Mhz and the new 406 Mhz (typically with a GPS locator signal). I did a Jim Weir-specified dipole with legs of 22.5" and 6.3" and installed it on back of the pilot seat. Looking at pictures of the Artex ELT 345, I see a BNC connector, so I made up an RG400 coax with one end a male BNC and the other split between center and sleeve, each soldered to the long leg of the copper foil tape. The short leg of the dipole was electrically connected with a conductive adhesive copper foil.