The mil encypted was always on a seperate frequency.
They did actually use the civi one as well to be able to adjust out atmospheric effects.
Mind you my knowledge is from being constripted due to knowledge of newtons laws and pocessing a scientific calculator on a gun position to the command post when the lay computer went tits up.
SMIG Badger Finnch and BSM Murphy I think there names were, after the intial "I don't care if your a sapper son" followed by a belt round the head with an A4 binder gave me a crash course in position fixing, firing out the errors, cresting and other such gun bunny perversions. Easy week with a rover full of survey gear out the window. Swapped for "confirm" "confirm" "down safety" "No 1 gun, 5 rounds fire for effect down safety fire!!" noisy bastards.