Proportional Radio Control

Yes, you will need to have a fixed resistor and switch to simulate a pot.
For example, steering a model:

X1 - 4K7 resistor - X2 - 4K7 potentiometer - X3 - 4K7 resistor - X4

Connect a NORMALLY OPEN switch between X2 and X3
Connect a NORMALLY CLOSED switch between X3 and X4

Use X1 and X4 as the new joystick, but only two switched.
Use the 4K7 potentiometer to adjust the steering straight ahead.

This will give you normally straight, and two switches: one for left and one for right.
You may need to change the values of the resistors, depending on the unit you are building. The above assumes you use a potentiometer with an "active rotation" of 20K Ohms.

R/C units may have a 100K potentiometer, but the pot has 100K over a 300 degree rotation. In your R/C transmitter it only uses 60 to 90 degrees for the joystick. That is only about 20K Ohms (maybe 30K).

BR Harry

Thank you for respose. So, if I use push button for this project does it need different resistance for fixed timming resistor each channel?

Yes,
The potentiometers can be replaced with push-buttons (with fixed timimg resistors).
Yes, you can press several buttons simultaneously operate more than one simultaneous function.

BR Harry

I have question about this project: Can we replace the potentiometer with push button. If we can then can we push more than one button at the same time?