Hello!! Sorry for my English i'm an Italian guy.
With this tutorial you can convert any radio whit a ppm signal in fm (40MHz 35MHz 72MHz) in 2,4GHz whit any module.
I have converted my jr-MX-12. This transmitter is without the external module, the Tx module is internal.
There is the DIY module for convert the Radio but it isn't necessary.
You only need a Tx module with its pin-out scheme.
how can I find his scheme? If you use a futaba module you need to search in google "futaba module pin-out" for image.
I used a OrangeRx module for the Turnig Tranis.
Step 1: PIN OUT Tx SCHEME
This is the pin out of a Turnigy Taranis. I have bought the Orange Tx module "OrangeRX DSMX DSM2 Compatible 2.4Ghz Transmitter Module V1.2". This module is compatible with JR, Turnigy and Taranis. Then search Taranis Pin Out in google, the Pin Out of the module is the same of the radio.
I need only 3 wire (this module have the integrated antenna): PPM, Ground, VCC.
Step 2: My Tx
The hard part is finding the PPM signal in the old Tx Module inside the tx.
Also hear google can help we. Search for image "PPM" and the name of the Tx. In this case i have search "PPM MX-12" and i have find this image. (masse is the ground).
Step 3: Cut & Weld
Cut the three wire of the signal, then remove the old Tx module.
Weld 3 extension wire.
Then weld 3 jumper wires and mark the wire. In my case, the green is PPM signal, the orange is the VCC and the orange-White is the ground.
Step 4: Cut the Radio
Now take with a sheet the dimension of the module and cut the radio. You need make a big hole for accommodate the new Tx Module. Pay attention: the hole need precise. If is to big the module falls. If is to small, you can't insert the module.
Then put the module inside.
Step 5: Connect and Try
Now connect the extension wire in the module. Mount the radio and all is done, you can try the radio.
Why i wont convert my radio to ghz?
An Rx 2.4ghz cost 9€, an Rx in fm cost 20€ and you need a crystal (15€)
The signal 2.4ghz is without disturb, and you can fly with other people in safety.
Why i wont use a normal module and not a DIY module?
Because the DIY is weld inside the radio, with a normal module, in the future, i can change my module with (for example) a open lrs 433. With this connection method (3 Wire) i can use ANY module because every module use a PPM signal, a VCC and a GND. I can use futaba module, jr module, tranis module.. ecc..
The only restriction is: The module need have the build in antenna!!!