AN/GRC-9 equipment is for HF (high Frequency) use and would have been used for some line of sight, and, beyond line of sight communications. The frequencies used by this equipment has the capabilities of world wide communications under prime atmospheric conditions.
From Tom Norris' page:
[AN/GRC-9] Radio set, 2-12 MHz Am, CW, RF power 3.5-15 watts depending on mode and power supply.
RT-77/GRC-9 tranceiver power supplies
GN-58/GRC-9 Hand Generator
PP-237/GRC-9 for 110 vac operation
DY-88 for 6,12, or 24 volt operation, or
BB-317 battery for portable use (receive only).
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