Radio msg codes AM### where is it?

[NeonsStyle]

Hey All,

I'm often getting contact reports from Bdu or other subs of
Convoys in Square AM351 or whatever number, but for the life
of me, I have no ideas where these grids are.

Is there a map somewhere that lays out the AM grid
pattern used by the Bdu radio messages?

Thanks

[Edit] Come on guys... someone must know what these AM### msgs mean in the
radio info? ie Contact in AM323 Course, speed etc etc Is there a map
that shows these grids?