The game has controls for Talk over radio and Talk over long-range radio. These controls can be found and changed in Settings->Controls->Common and under there in the Communication section.

As far as I understand the control for Talk over radio is specifically for talking through short range (hand held) radios and the control for Talk over long-range radio is specifically for talking through long-range (backpack) radios.
All in all these separate controls probably are for quickly changing between talking to the short range or the long range radio which is great.

To keep things shorter from now on I'll abbreviate the radios as follows: short range radio = SR, long-range radio = LR

The controls themselves work just fine but there's something that seems to be bugging when changing between radios using the dedicated controls.

The problem is that if you broadcast (using the dedicated controls) through SR then through LR and then again SR, it more often than not ends up so that broadcasting is done through LR, although it's supposed to be happening through SR. There are rare occurrences that after broadcasting through LR and then switching to SR the broadcasting happens through SR as it should but, like said these are rare occurrences.