Summary

Adapter to make use of different external antennas on the Frsky Taranis X9D. V2 has a slightly larger outside hole for more clearance on some antennas like the Frsky 7db patch.

There is now also a version supporting the Frsky rp-sma pigtail with 8,8mm thread length.

Instructions

To print the adapter you need to use support material. I printed it massive using Repetier/Slic3r on my Makergear M2.

This adapter need a slight mod to the lower TX case as shown in the photos (easy to do with a hacksaw and a Dremel).

It is designed around a RP-SMA-fm with 11mm thread lenght like this one from ebay: http://www.ebay.com/itm/RP-SMA-female-male-pin-crimp-RG174-RG179-RG316-RG188-Cable-Connector-/160864505174?pt=US_Radio_Comm_Coaxial_Cables_Connectors&hash=item2574458d56
I used RG316 coax directly soldered to the RF-board but you can of coarse use the thinner RG178 coax (both connectors can be found separately or as precrimped pigtails).
Then there is the choice to fit an U.FL connector directly on the RF-board and use a RP-SMA pigtail with an U-FL connector in the other end (this usually has the thinner RG178 coax).

In any case be very careful when desoldering the original RG178 coax so that you don't lift the center wire copper trace from the RF-board. I would say that unless you are quite skilled with the soldering iron and/or desoldering station, don't attempt this on your own; get someone qualified to do the solder-work on the RF-board.

You can find some more information i this thread on Rcgroups (see post #505 and onwards, and there is also some earlier in the thread): http://www.rcgroups.com/forums/showthread.php?t=1966664&page=34

It should go without saying that by doing this mod you risk the chance to fry the rf-card on the Taranis if you power up and run the tx without an antenna fitted to the sma-connector. Don't say I didn't warn you!

UPDATE 11 APRIL 2014 Frsky Taranis X9D Removable antenna adapter