Thanks every one,

I am grateful to all of you as your suggestions helped me a lot.

I put each receiver in a separate metal box
Used shielded wires for each i/p,o/p at receiver.
Inductor of 33uh in vcc line for each receiver

With these arrangements it seems (I observed) till now no indication of interference.

With ref. of FAQ & other suggestions I am planning to separate pcbs for controller & related circuits from receivers, but this will take some time to implement
before that i have one more doubt in this:
Is there any need &/or a way to use filter in ground path?


Thanks & Regards