1 M or m â prefix designating a number in thousands (not to be confused with SI prefix M for mega-or m for milli).
There are two types commonly referred to as: 'Shallow' and 'Deep' water. The differences are not only in the Frequency but also in the Beam Width and they are as follows: 'Shallow' water HST-WSBL 106-72 Transducer will operate on 2 frequencies on the HDS models: 200 (20Â°) & 83KHz (60Â°). 'Deep' water HST-DFSBL 106-77 Transducer will operate on 2 frequencies on the HDS models: 200KHz (12Â°) & 50KHz (35Â°).
Sonar manufacturers are building the sonar heads to match the capabilities of those transducers. Conventional sonar offers limited choices of discrete frequencies, usually 50 kHz for deep and 200 kHz for shallow conditions. Because CHIRP transmits a pulse that ranges across a portion of the spectrum, say 28 kHz to 75 kHz in each pulse, the transducers are a little more complicated.