They're using single sideband. Effectively their audio is just being shifted up to the moon frequency and back down again. (or, alternatively, like AM but with

They're using single sideband. Effectively their audio is just being shifted up to the moon frequency and back down again. (or, alternatively, like AM but with no carrier or secondary image) The amount of doppler depends on what frequency they are at and where the moon is. One can set an offset between RX and TX frequency, but one doesn't have to.