Re: How about fish finders? and speaking of periscopes...

[protek@shreve.net]

    About the fish finders...  I have mounted one on my sub looking down
and forward also.  They do work and will take probably much more than 50
feet of depth.  However, one caution.  Most have automatic gain control in
one form or the other.  If looking forward and they do not see the bottom
they turn up the gain.  This results in very very sensitive reception.  I
once noticed that I kept seeing 18 feet on mine even when I was moving.  I
looked at the depth gage and I was 18 feet deep.  It was so sensitive that
it was recording surface echos.  Get one you can set to a manual gain
value.  Problem is this; every time you turn it off you have to go and
reset it and it takes a minute or two.

Gary Boucher