Experiments in airborne BASIC—"buzzing" computer code over FM radio

My dad and a friend used to transmit TI-BASIC programs to one another late at night over the 2-meter HAM band back in the mid 80s. They both had TI-99 computers with "tape drives" (really just a regular tape player set next to the computer) and microphones. One would key the mic on the HAM radio and hold it next to the tape player's speaker and the person on the other end would hold the radio speaker next to the TI-99's mic input. They shared code and collaborated on a few projects this way.

I remember it well; in NL we used to have those radio programs but also plastic 'flex' records you would put on your record player connected to your computer. You would be able to run the Basicode on any supported computer which gave you the ability to share between C64 and MSX for instance; http://en.wikipedia.org/wiki/BASICODE.

How could the data not be lost? Especially when this equation involved an FM broadcast, a commodity FM receiver, and then a microphone to record the FM output to a cassette tape. Can someone with a better understanding of these things explain to me why this didn't come out as nonsense?