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After almost 20 years of service I decided to buy a new Radio Transmitter. Since the FC18 is still in use I was actually caught by the limitations when it comes down to the mixer and training function. The price these days is very competitive and for less dollars you've got more functions and more possibilities to extend. Below a short summary on the modifications done on the 9XR. Since the 9XR radio comes without the RF module I decided to build in a FrSky Telemetry module. The main reason is that I want to make it compatible with the other models and their receivers. I followed the same approach, done with FC18 : make an adapter , so called mainboard on which the FrSky Module can be fitted. All required connections should be taken from this main board. Two additional small PCB's were added to the design in order to wire out the two-color LED and the bindswitch. These two PCB's need to be separated from the main PCB.  Further the design remains the same ; RS232 levelshifter and LDO power supply to derive 3.3V from the FrSky module for external circuitry. (up to 100 mA max.).  After a few days of waiting I finally received the bare boards, ready to populate them with the components.
3D Design of FrSky module on main PCB	Bare Printed Circuit Boards before assembly
The pictures below show in more detail the steps taken in order to install the FrSky module inside the Turnigy 9XR radio. First modification is the battery connection. Unfortunately the length of the wires on the balance connector of a standard Turnigy 2.5A nano tech is too short. Therefore the battery is lifted up and the cover of the 9XR cannot be closed. Since only two connections are used (the individual cell voltages do not reach the main PCB of the 9XR). I decided to extend only positive and ground, by using a spare connector.
The two center pins are not connected to the main PCB. Therefore only the outer two can be used to power the 9XR.
Components mounted on main PCB, LED PCB and SWITCH PCB already separated.
FrSky Module mounted on main PCB
This piece of metal does not do much : the throttle stick should have a proper feeling, so modification required !!
This piece I was after (taken from my Futaba FC18, since it was not used on the right stick)
Much better !!!
To remove the internal antenna the plastic module has to be taken out
I used a small drill to locate the exact position for the new external antenna
The real work :  make sure to use a low RPM on your dremel to avoid melting the plastic
External Antenna mounted in place
We are going to put the "dot"on the I, this location is for the bi-color LED
Bi-color LED in place and "waiting"for the LED PCB to ber glued in place.
LED PCB installed, note the hole for the switch PCB, to be installed after the LED PCB.
Switch PCB installed into position prior to solder the switch on the PCB. This prevents mis-alignment
All components wired and installed
Remove of the internal plastic bay for the original RF-module
Unlucky, cause the edges are hard to reach using the dremel ; cutting on two sides is required
I made a new cover backplate from black FR-4 material
Back cover glued in place (I used 5 min. Epoxy)
After flipping the transmitter upside down and back the glass front plate came loose, next glue should be better Turnigy ! I took it completly off and used adhesive tape (double sided) after i cleaned all surface where it should stick to.
This should hold it better in place ; make sure the surface is clean before sticking it back
DONE !!! ALL hardware modifications in RED