The rule is higher frequency for shallow depths. Low frequency for large
depths. At your depth, the lowest power with short pulse length and highest
pulse recurrent frequency is best. Be sure to calibrate with lead line at
installation. Install straight down.
Steve


"mark" wrote in message
oups.com...
I am going to buy a sounder for use in my aquaculture operation. I
need it to be as accurate as possible in determining if my mussel
socks are touching the bottom or are 1' off the bottom. The water is
only 20 feet deep and it is a mud bottom. Some people are using SiTex
106-L which has 300 watts of power and 50 or 200KHz and some are using
Furuno FCV 620 which has 600 watts of power and I saw one with a
Hondex. For my application is there any advantage of one over the
other? Also My boat is aluminum and some dealers are telling me to use
a bronze transducer but make sure it is isolated with plastic bushing
and other are saying use a special ordered aluminum transducer. And
finally would it be most accurate if it pointed straight down or would
having it 10 degrees off to one side (flat against the hull) make a
big difference, if so could I fabricate a level flat spot on the hull
to mount it to but would this create to much turbulence for it to read
properly? I want it as far forward as possible not on the stern. Thanks