There are two that I know of. The typical Millitary Academy does not have a radio station, at least not an FM. There might be a few shortwave relays out there; to be honest I didn't look.
It's like college radio, but with a General Manager like the seargant from movie Platoon. 89.3 WLJP West Point Millitary Academy has a radio station, it's format is Christian Contemporary. http://www.soundoflife.org/ Now, we all know that a millitary academy is not a branch of government. However, seeing as we don't have any rogue militias circulating our cities (except the Guardian Angels) It's very clear the graduates here that move on to work in the military usually opt to work for the U.S. military.
I was going to get into a whole liberal speil here about the weird connection between evangelical Christianity and the military but it's been pretty hashed out elsewhere. So we'll cut right to the arcanity...
Since there has only been only one other radio station based at a millitary academy, WHWE 88.7 Howe Military School Sturgis, MI. I don't have a big powr point presentation to prove conspiracy. In fact Howe Millitary school is defunct. The station still exists, still running an upsold Class A from D license at a mere 100 watts. They operate as a pseudo-community station mostly running syndicated christian programming like Mary K. Shanahan.
West Point does have a great Amateur Radio Club. Its current call sign, W2KGY. It began in 1926 having been founded by LT William Holmes Wenstrom with the call letters 2CX. But before that club was even started They also ran another station WUAH as early as 1922.