Re: [PSUBS-MAILIST] Re: SONAR

[Ed Greany <crest25@attglobal.net>]

Yep, you're correct. Sonar will bounce or deflect with a change in
medium or gradient temperature layer. I didn't comment about it bouncing
or now off the surface since I have never tried that. I only know about
signals going down or out from the vessel.

Ed

Adam Lawrence wrote:
> 
> 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
> > >
> >