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).

A lot of talk here of audio signal generators.

Although depth sounders are referred to as "sonar" they do not work at audio
frequencies.

Hi-Fi equipment can work up to 20K (salesmen and status-seekers will clain
more)
This is the upper level for people with good hearing. By the time we can
afford boats and gadgets out hearing has deteriorated to much below this.

Modern depth sounders work at 200K. This is radio frequency.

Some years ago the most popular channel on BBC radio was on 200k. It would
seem that, if you wish to test your fishfinder, you might be better off
using a thirty year old European broadcast receiver and hold the antenna to
the transducer.

Henry

On Tue, 13 Jan 2004 23:53:39 GMT, "Henry" wrote:

A lot of talk here of audio signal generators.

Although depth sounders are referred to as "sonar" they do not work at audio
frequencies.

Hi-Fi equipment can work up to 20K (salesmen and status-seekers will clain
more)
This is the upper level for people with good hearing. By the time we can
afford boats and gadgets out hearing has deteriorated to much below this.

Modern depth sounders work at 200K. This is radio frequency.

Some years ago the most popular channel on BBC radio was on 200k. It would
seem that, if you wish to test your fishfinder, you might be better off
using a thirty year old European broadcast receiver and hold the antenna to
the transducer.

Henry



It depends on how you propagate it whether it is audio or RF.
If you are transmitting audio you are transmitting an acoustic wave.
If you are transmitting RF then you are transmitting an
electromagnetic wave.

You can have RF transmitted easily at 10 khz. You can also have audio
at 10 khz, as an example.

A depth sounder transmits audio. An acoustic wave.

Although you could use an RF signal generator to test a transducer, if
the signal generator went down that low. Most do not.

While most better audio generators go up to about .5 mhz. Probably
easier to find than an RF generator that covers that range.

Yes RB, you have it correct as how to hook it up to the coax.
50 to 200 khz range will probably be where you find them. There are a
few that go up to 400 khz.

If I remember right 50 was common, 80, 120 or 125, 180, 200.
50 and 200 were the most popular. I may be wrong on some of the other
frequencies. Maybe some more that I have forgotten too.

Regards
Gary

It depends on how you propagate it whether it is audio or RF.
If you are transmitting audio you are transmitting an acoustic wave.
If you are transmitting RF then you are transmitting an
electromagnetic wave.


Thank you, this makes sense.
I was trained in radio and perhaps was being too simplistic. Yes, I was not
differentiating between acoustic pressure waves and EM waves. I should study
the workings of the transducer. Can anyone help here?
Does a transducer have a diaphragm vibrating at 200K?

I must confess that my training started over 50 years ago (in the RAF). It
was much simpler then (fishfinder, what's that?), and I now feel rather left
behind.

Henry

The early Seafarer (Flashing neon) sounders in the UK ran at 150kHz.


"Gary Schafer" wrote in message
...
On Tue, 13 Jan 2004 23:53:39 GMT, "Henry" wrote:

A lot of talk here of audio signal generators.

Although depth sounders are referred to as "sonar" they do not work at
audio
frequencies.

Hi-Fi equipment can work up to 20K (salesmen and status-seekers will
clain
more)
This is the upper level for people with good hearing. By the time we can
afford boats and gadgets out hearing has deteriorated to much below this.

Modern depth sounders work at 200K. This is radio frequency.

Some years ago the most popular channel on BBC radio was on 200k. It
would
seem that, if you wish to test your fishfinder, you might be better off
using a thirty year old European broadcast receiver and hold the antenna
to
the transducer.

Henry



It depends on how you propagate it whether it is audio or RF.
If you are transmitting audio you are transmitting an acoustic wave.
If you are transmitting RF then you are transmitting an
electromagnetic wave.

You can have RF transmitted easily at 10 khz. You can also have audio
at 10 khz, as an example.

A depth sounder transmits audio. An acoustic wave.

Although you could use an RF signal generator to test a transducer, if
the signal generator went down that low. Most do not.

While most better audio generators go up to about .5 mhz. Probably
easier to find than an RF generator that covers that range.

Yes RB, you have it correct as how to hook it up to the coax.
50 to 200 khz range will probably be where you find them. There are a
few that go up to 400 khz.

If I remember right 50 was common, 80, 120 or 125, 180, 200.
50 and 200 were the most popular. I may be wrong on some of the other
frequencies. Maybe some more that I have forgotten too.

Regards
Gary

In article 7y%Mb.83359$X%5.9293@pd7tw2no, "Henry" wrote:

Modern depth sounders work at 200K. This is radio frequency.

Well, maybe, but not for sure. Common sounder Frequencies a

50 Khz
88 Khz
100 Khz
200 Khz

Most of the consumer type sounders are 200Khz, that is true,
but there are a whole slew of different types and they use different
frequencies, depending on the typical use.

Bruce in alaska
--
add a 2 before @