RF module bay "JR-Style" for Multiplex MC3010/3030/MC4000 for ELRS, Radiomaster Ranger micro , 4-in-1 RF module etc.

With this Thing and some basic electronics know-how, it is possible to provision an old-fashioned 90´s MC3010, MC3030 or MC4000 RC transmitter with an external JR-type RF module bay.
In my case, I am using it in combination with a radiomaster ranger micro 2,4GHz ELRS RF module and a CR-1 board (ppm/Sbus --> CRSF, some 6€ at Aliexpress) as "translator" between the protocols.

What is needed:

• the printed part (obviously)
• a suitable RF module (obviously - in my case a radiomaster RANGER micro 2,4GHz ExpressLRS)
• a 5-min RM2,54mm pin header with LONG pins (in my case, 2 pins are NC, so 3-pin would also work)
• a 5-pin 180° DIN audio connector (male)
• conversion electronics, depending on RF module type (in my case, CR-1 ppm/SBUS to CRSF converter)
• Some hot glue or other method of fixation for the DIN plug and the header
• a bit of wiring (3 pins, some 12cm distance to be bridged)

I am mentioning here that it may turn out to be a little difficult to perform the binding procedure between receiver(s) and RF module when installed on the transmitter. It may be possible by setting the right bindphrases manually in ExpressLRS configurator (havent´tried this) - I did the binding by temorarily moving the RF module into a TX-16S transmitter, doing the binding there and then relocating it to my 3030 - this worked perfectly.

Mechanically, this is a snug fit into the 3030, and also a good and safe snap-in of the RF-Module into the adapter - no tools required.
It fits a "naked" Multiplex MC3030 and most likely also MC3010 and MC4000 (which have nearly the same housing). It is compatible with the hand rests, but very probably NOT with the bulky transmitter tray or space box.

The PPM signal as well as power supply and 35MHZ RF disable pin are accessible at the 5-pin DIN connector - so everything you need is accessible, no external supplies etc.
There is a small space in the adapter where wiring and CR-1 board (or for example an arduino nano or ESP32 board, if you use the adapter for other modules) find sufficient space.

With this adapter/RF solution installed, the buddy box trainer cable is not accessible, as it uses the same connector.
Programming wise on the MC3030, you will ideally move the servo centres by some 10-12% to account for the different neutral pulse (16 instead of 1,5ms).
Due to the one-way-street nature of the link between transmitter and RF module, there is of course no telemetry or downlink of any kind accessible from the MPX transmitter´s user interface.

Pinouts of the connectors (RF module and 5-pin DIN connector of MC3030) are widely available on the internet.
Please consult your local RF legislation before activating this modification to your transmitter.

Share and enjoy, and don´t blame ME if you mess this up and fry your old transmitter.