In article 7y%Mb.83359$X%5.9293@pd7tw2no, "Henry" wrote:

Modern depth sounders work at 200K. This is radio frequency.

Well, maybe, but not for sure. Common sounder Frequencies a

50 Khz
88 Khz
100 Khz
200 Khz

Most of the consumer type sounders are 200Khz, that is true,
but there are a whole slew of different types and they use different
frequencies, depending on the typical use.

Bruce in alaska
--
add a 2 before @