Re: [PSUBS-MAILIST] Re: SONAR

["Adam Lawrence" <adteleka@in-tch.com>]

I don't know much about sonar but I do know about ultrasonics with respect
to UT or weld inspection. When sound moves through steel,  plastic, or
whatever it moves at a relatively uniform velocity for the specific medium.
When the sound wave reaches a point where the medium changes, like air on
the other side of the steel plate, most of the wave is reflected back to the
source. I would think that sound would reflect off the bottom and off the
surface in a similar manner since a change in medium (velocity) has
occurred. As far as the sonar device needing to be calibrated for that
application, I don't know.
Adam L.
----- Original Message -----
From: Matt Cadieux <compkid15@earthlink.net>
To: <personal_submersibles@psubs.org>
Sent: Sunday, August 12, 2001 10:21 PM
Subject: Re: [PSUBS-MAILIST] Re: SONAR


> In order for a sonar to work it has to "hit" against something and bounce
> back so an upward facing sonar would only give you readings if you were
> under something.  SO it would only really be good to check when your
> surfacing to make sure that your not coming up under a boat other then
that
> it would give no reading.
> ----- Original Message -----
> From: "Ed Greany" <crest25@attglobal.net>
> To: <personal_submersibles@psubs.org>
> Sent: Saturday, August 11, 2001 3:13 PM
> Subject: Re: [PSUBS-MAILIST] Re: SONAR
>
>
> > Good question. The answer is no, now unless they are both on the same
> > frequency.
> > The received is tuned to receive a certain frequency (range) and it is
> > listening for its own bounce.
> > It's like two radio operators standing next to each other talking to
> > someone on the other end. The two radios do not mix and confuse the
> > receivers.
> >
> > Ed
> >
> > Michael B. Holt wrote:
> > >
> > > What problems appear if one uses TWO fishfinders: one pointed down to
> > > give distance below the keel and one pointed up to give distance to
> > > the surface?  Would the two interact to produce false readings?
> > >
> > > Mike
> >
>