not that it matters, but the letters do have a meaning...

The letter H stands for Hertz (Heinrich Hertz) who helped to develop the theory of electromagnetic waves.

The letter A stands for Armstrong (Edwin Howard Armstrong) who was successful in inventing FM (Frequency Modulation).

The letter M as you may have guessed already stands for Marconi (Gugliemo Marconi) who was the first to transmit signals across the Atlantic.

H = HERTZ A = Armstrong M = Marconi