I'm indicating where a characters voice is coming from and I want to know, do I need to keep repeating on every bit of dialog? Is it acceptable to provide this parenthetical on the first bit of dialog and then not mention again unless the situation changes? Here an example:

CHARACTER A
(via suit radio)
I'm in a space suit talking through the radio!

CHARACTER B
(via comms)
I'm talking through the ship's general communications system!

CHARACTER C
Why are the two of you yelling?

CHARACTER A
(via suit radio)
I'm not wearing the earpiece so I can't hear you!

In the deathless sequence above, is the bolded parenthetical needed or can I avoid repeating the parentheticals throughout the scene?

TIA

Personally I'd write it as follows

A scratchy voice comms through on Character As Suit Radio unit.

                                  Character B (V.O.)
                 A, you there?


You could also do it as you've suggested, but use (V.O.) for all dialogue for the character and parantheticals just for the first time.

First, add the VO as Anthony indicated.

For me - I only use the parenthetical once for each character - I think after that the reader gets it.