i have a (Ham) Amature radio type question

[mr_fixer]

I am listening on shortwave tonight and i heard something i don't hear very often. Morse code over Am modulation. Its a AM broadcast somewhere around 5900 Khz using a 1khz tone to transmit code. Why would someone do this? its very wasteful on power. It would be better just to send switched CW. Unfortunately i can't copy code to see what they are sending. but they have been transmitting for over a 40 mins now. Logan