By Rx I mean the receiver that is located in the tank. And no you can use mode 1 or mode 2, here in the USA we mostly use mode 2.
CCPM stands for Cyclic/Collective Pitch Mixing, this is what is programmed into the Esky 6-channel radio that you are using and will make it unuseable for your tank. When you move the throttle stick up on the radio 2 things will take place 1)the motor speed increases, and 2)the channels marked with Aileron, Elevator and Pitch(Aux) will also move the servos controlling the swashplate on the helicopter. The mixing of the 4 channels is tied to movement of the ratcheted stick which is usually the throttle stick in heli radios.
In short what I am saying is that the Esky 6-channel radio that you are attempting to use for a tank will probably never work because the radio is permanently mixed for use with helicopters and is unsuitable for use with anything else.
I suggest you use a non-helicopter radio or if you can get a computer radio that will support different model types get it.
Good luck,
DT