72 MHz to 2.4 GHz RC Radio Conversion

Before modifying anything I recommend testing the 72/35 MHz connection with an existing RC model. Knowing the default radio/receiver configuration works can be helpful later on when troubleshooting any modifications you make to the radio.

Test all the channels and try some long range tests, this shouldn't be a problem if you have been flying already.

Remove the antenna, channel crystal, and front face of the radio if possible to more easily access the circuit boards.

Now remove the screws on the back, and unscrew the trainer port so that you can fully separate the front and back case sections.

There are three connections that you will need to identify:

1. Voltage, or V+

Use a voltmeter to find the voltage. Look near the battery or switch, and look for the larger solder connections.

2. Ground

Labeled in several places on my radio, you may need this to ground the voltmeter when measuring voltage.

3. PPM, which is the transmission signal sent through the crystal to the receiver.

If possible use an oscilloscope to find the PPM signal. I did not have one but did some searching online and found that someone already identified the connections.

Many radios have an entirely separate circuit board dedicated to 72/35 MHz transmission. If you can find this board the job is much easier since you can just find the wires connected to it. There should be at least three wires going to this board.

First I would recommend drawing a rough circuit diagram so you have an idea of what connections to make.

Once you have a good idea of where your connections are, begin soldering the wires into the radio and switch connections.

You will also need to solder the antenna wire onto the 2.4 GHz module. Solder the inside portion of the antenna to one solder pad, and the outside section to the other solder pad.

For this project, I tried to completely isolate the power and PPM signals between each module frequency with the flip of a switch. I was not fully successful due to having to remove the crystal for 2.4 GHz mode. In the future I would like to figure out how to completely isolate the power from the 72 MHz mode to cut down on battery consumption when using the new module, and to allow the crystal to be installed when in 2.4 GHz mode.

Before assembling anything or making permanent modifications to the radio I highly recommend testing everything first. This allows you to make changes or troubleshoot while everything is accessible.

Test all channels up close and at long range.

If everything checks out then move on to the next step!

Begin this step once you are sure both modules work.

Use the provided template to drill holes for the binding circuit in a good location. Use 5/32 or 11/64 inch drill bit for the LED and button holes, and use a 5/64 or 3/32 inch drill bit for the screw holes. This kit comes with six nuts and two screws. Use one nut on each screw to secure them to the radio case. Then use the other nut to adjust the height of the circuit board, install the circuit, and use the remaining nut to clamp the board to the previous nut. Tighten them together to hold the binding board in place.

Use a 1/4 inch drill bit for the switch and antenna holes.

Mount the module, wires, and antenna to the radio case or radio circuit board with hot glue or epoxy. This is a little tricky because the radio case must be partially closed due to the wires already being soldered on at this point. If mounting anything to the radio circuit board, make sure to use a thick piece of plastic to separate them before gluing.

Once everything is connected and mounted, test both modules again before final assembly.

Close up the radio case (slowly) using a light to make sure nothing is being crushed or blocked by the newly installed module and wires. Glue or bend any remaining wires so they are out of the way. Check the stick movement to ensure nothing is blocking their range of motion.

Now install the screws on the back.

Before installing the original antenna, look into the hole to make sure no wires are blocking the passage.

Install both antennas, the transmitter crystal, and the battery (Leave it unplugged when not in use).

I scoured the web for hours trying to find information specific to my model and found many great resources along the way. You may need a few more specifics than I can provide in my Instructable for your radio model. Here are some resources I found that will hopefully make this process easier and save you some time.

Converting old transmitters to 2.4GHz using 'hack' modules

Futaba T6X upgrade to 2.4Ghz with the Corona 2.4Ghz DIY Module (DSSS) CT8Z

Airtronics VG6000 2.4 ghz conversion

Help with Frsky into Airtronics please

Adding a Corona 2.4gHs system to a old 72mHz JR TX

Sanwa RD6000 Super Conversion to Frsky 2.4GHz

Video - Flite Test - DIY 2.4Ghz Radio Upgrade - FLITE TIP

Corona DSSS V2 Hack Thread

Assan 2.4Ghz X8D hack

Frsky added to rds 8000

If using an older radio, I highly recommend upgrading the battery to a Lithium Iron (LiFe). At 9.9 volts, it is designed for radios, but you need to make sure that your charger is able to charge these. Also, don't try charging this new battery with the default wall charger that comes with the radio.

All done!