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Varioprop Conversion

Here I want to show you, how I converted an old Graupner Varioprop transmitter to 2.4 GHz.

I didn’t want to have another transmitter with all kinds of bells and whistles. My intention was, to make an old transmitter usable again that was laying around in my cupboard. I have other radios that can do everything. On the other hand, I wanted to improve my programming skills for the Arduino microcontrollers.

As I wanted to use this transmitter especially for my new SFC-Stick, I limited the number of controls to four (throttle, rudder, elevator, ailerons). The two extra potentiometers in the center were not yet connected to the controller and the 3-position switch was not used in the program.

First, I removed all the electronic components, the antenna socket and the battery until only the mechanical parts (sticks) remained. Then an RF Module from FrSky (V8HT) was inserted. The new antenna socket was glued in with epoxy. Also, a new charging socket and a new on-off-switch were necessary. The battery is a 2-cell LiPo of 800 mAh which is absolutely sufficient. The transmitter now has a very low weight (670g ~23.6 oz).


The PPM signal is provided by an Arduino Pro Mini.

You can find my sketch here: rc_encoder_sfc_stick

There is no display or keypad in the transmitter. If I want to change the program, I have to connect the Arduino to my PC and upload a modified sketch.

I use this transmitter specifically for my SFC-Stick model, which I have presented in another post.