[BC] Question on Call Letters

[PeterH5322]

>In Amateur Radio, we have callsigns in the USA that start with A, K, N and  
>W, and some government utility HF stations' callsigns begin  with K, N and 
>W.  
>Is this the same with broadcast stations?  If  we were ever to run out of K 
>and W callsigns (probably unlikely, but just for  the sake of the argument), 
>would the FCC issue broadcast callsigns starting with  A or N?

K--- and W--- for broadcast stations; N for aircraft stations (which 
always corresponds to the aircraft's registration number). I we run out 
of four letter calls, we'd go to five, as has Mexico.

I would guess that N prefixes were intended for Navy stations and A 
prefixes were intended for Army stations.

NAA was a Navy medium wave station, pre-NARBA. 690 kHz, Arlington, VA.

Given the NAA call, perhaps this was the first and only Navy medium wave 
station. I know of no corresponding Army medium wave station, AAA.