flywheel diode for radio transmitter and receiver need? or not?
Extremely unlikely that you need the diode, however you should be using a high-side switch (don't break the RF ground) and there may be a problem if you are applying a non-zero signal to the data in pin with no power applied. 

Consider changing to a high-side switch, adding a series resistor of perhaps 4.7K and a Schottky diode from data in to the transmitter supply Vcc. 

See other examples in SE for high-side switches, there are many.