Stubby wrote:

The explanation I got seems better: The atmosphere attenuates some
radio frequencies more than other (I believe high frequencies are
attenuated more than low, but it may be way more complex.) A lighting
flash is an impulse and thus, has all frequencies present at the same
level. The distance sensor can measure the level of 2 frequencies and
derive the distance. In practice I've heard that 6 frequencies are used
but that implies 36 amplitude ratios are being used.

Ding ding ding ding ding ding! Finally someone responded with the correct answer.

Dave