W/T and R/T from Swordfish
All aircrew received signals training, so the Observer could transmit, but perhaps not as efficiently as a TAG. When a long range tank was fitted, the Observer would pysically occupy the TAG's seat so would be able to use the wireless set in the rearmost seat.
Range would depend on the transmissions freq and power. This is beyond my knowledge, and anyway the freq would be different depending on the Carrier, and Fleet.
I think you need to make some enquiries of the Fleet Air Arm Museum, or Navy Historical Branch. Whole question of signals and radio and impact this had on fleet ops is sadly neglected.