Just found a couple of old transducers tucked away in a desk drawer in my
workshop. No clue as to what they're from, make, model, etc, nor as to
operating frequency.

If I recall correctly, the freq is the most important characteristic. Also
seems like the other thing is not to stick 'em on some depth finder that
overpowers them and pops the circuit that fixes the freq. Is all this
correct?

If so, what's some practical, reasonably simple way to determine their
design freq?

On Mon, 12 Jan 2004 23:26:00 -0600, "RB"
wrote:

Just found a couple of old transducers tucked away in a desk drawer in my
workshop. No clue as to what they're from, make, model, etc, nor as to
operating frequency.

If I recall correctly, the freq is the most important characteristic. Also
seems like the other thing is not to stick 'em on some depth finder that
overpowers them and pops the circuit that fixes the freq. Is all this
correct?

Yes - it's a question of how much current the crystal can handle in
terms of RMS power from the signal transmitter - if they are older
transducers, it's a pretty safe bet they will handle 600 watts.

If so, what's some practical, reasonably simple way to determine their
design freq?

Jeeze - those can be anywhere from 25 to 200 Khz. depending on their
age and what they came off of.

Are there any identifying marks on them?

Later,

Tom
S. Woodstock, CT
----------
"My rod and my reel - they comfort me."

St. Pete, 12 Lb. Test

No marks whatever. That's why I am trying to figure out some simple,
practical way to figure out what the design freq is. Nothing comes to
mind, though.

On Tue, 13 Jan 2004 10:39:15 -0600, "RB"
wrote:

No marks whatever. That's why I am trying to figure out some simple,
practical way to figure out what the design freq is. Nothing comes to
mind, though.



If you have a variable audio generator, hook it to the transducer.
Place an AC voltmeter across the transducer and slowly tune the audio
generator around the the most common frequencies that the transducer
could be. You should see a sudden rise in the voltage when you hit the
frequency.

Regards
Gary

OK. Great idea. That should work. I think most of those old units worked
freqs from approx 50-200khz. Don't remember any outside that range for
small personal watercraft.

On Tue, 13 Jan 2004 18:45:34 GMT, Gary Schafer
wrote:

On Tue, 13 Jan 2004 10:39:15 -0600, "RB"
wrote:

No marks whatever. That's why I am trying to figure out some simple,
practical way to figure out what the design freq is. Nothing comes to
mind, though.

If you have a variable audio generator, hook it to the transducer.
Place an AC voltmeter across the transducer and slowly tune the audio
generator around the the most common frequencies that the transducer
could be. You should see a sudden rise in the voltage when you hit the
frequency.

Interesting, but how would you hook the unit across the transducer
without taking it apart?

Later,

Tom
S. Woodstock, CT
----------
"My rod and my reel - they comfort me."

St. Pete, 12 Lb. Test

}}} Interesting, but how would you hook the unit across the transducer
without taking it apart? {{{

If I understand the question, you would simply put the audio generator and
ac voltmeter across the coax lead at some point (between the braid and the
center).

In article ,
"RB" wrote:

Just found a couple of old transducers tucked away in a desk drawer in my
workshop. No clue as to what they're from, make, model, etc, nor as to
operating frequency.

If I recall correctly, the freq is the most important characteristic. Also
seems like the other thing is not to stick 'em on some depth finder that
overpowers them and pops the circuit that fixes the freq. Is all this
correct?

If so, what's some practical, reasonably simple way to determine their
design freq?



Most of the Professionals would use a Signal Generator, Scope, and
Impedance Bridge, and then sweep the transducer to determine its
design frequency. Shoudn't be to hard if you got the test equipment.

Bruce in alaska
--
add a 2 before @

My situation is a little different. I've got a boat built around 1960, it's
got a thru-hull transducer with no markings. Presumably it's a little more
modern than 1960's!
Assuming that I can estimate the resonant frequency ( I've got only a
frequency generator and a decent multimeter, ) how do I decide if it's worth
while getting a plug to adapt the transmitter to my Lowrance X48?

Or do I just wait a year until I pull the boat out of the water for annual
maintenance and fit a new thru-hull transponder?
Regards
David
"Bruce in Alaska" wrote in message
...
In article ,
"RB" wrote:

Just found a couple of old transducers tucked away in a desk drawer in
my
workshop. No clue as to what they're from, make, model, etc, nor as to
operating frequency.

If I recall correctly, the freq is the most important characteristic.
Also
seems like the other thing is not to stick 'em on some depth finder that
overpowers them and pops the circuit that fixes the freq. Is all this
correct?

If so, what's some practical, reasonably simple way to determine their
design freq?



Most of the Professionals would use a Signal Generator, Scope, and
Impedance Bridge, and then sweep the transducer to determine its
design frequency. Shoudn't be to hard if you got the test equipment.

Bruce in alaska
--
add a 2 before @

On Wed, 14 Jan 2004 21:55:45 +1100, David Flew wrote:

My situation is a little different. I've got a boat built around 1960, it's
got a thru-hull transducer with no markings. Presumably it's a little more
modern than 1960's!
Assuming that I can estimate the resonant frequency ( I've got only a
frequency generator and a decent multimeter, ) how do I decide if it's worth
while getting a plug to adapt the transmitter to my Lowrance X48?

Or do I just wait a year until I pull the boat out of the water for annual
maintenance and fit a new thru-hull transponder?
Regards
David

I'd suggest you wait until you pull the boat out of the water and replace
it. The problem is that you can't identify it. Others have suggested ways
to determine the resonant frequency, but that won't tell you how much peak
power it will handle. I don't know how you can do that without destroying
it.
--

Larry
email is rapp at lmr dot com