RE: NIMH receiver batteries charge with NICD charger that comes with TX/RX?
The charger that comes with the radio is generically referred to as a WallWort. It usually charges at 50ma to 100ma. This is essentially a Trickle Charge for larger NiMh batteries. You charge for 18 hours and you should be fine.
With a better charger that has Peak Detection and the ability to Cycle the batteries, you have much more control over how the batteries are charged and conditioned.
Monitor the voltage of the batteries, under load, with a good ESV, and you should be OK.