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

On Wed, 14 Jan 2004 01:52:31 GMT, "Henry" wrote:


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?

Yes - actually, a piezoelectric crystal that vibrates at the operating
frequency.






--
Peter Bennett, VE7CEI
peterbb (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

In article .com,
Peter Bennett wrote:

Yes - actually, a piezoelectric crystal that vibrates at the operating
frequency.

True, actually 90% of the piezoelectric crystal tranducers are Barium
Titanate Crystals and most of these are made by one company. (I forget
the name now, but they OEM to all the Sounder producers) The 28Khz
Transducers are Magnetic Restriction types and not crystals, and the old
WWII SubSignal "Big Whoppers" were also Magnetic Restriction types as
well. It's really hard to get crystals to resonate below 50Khz with the
power levels used by typical sounders below that frequency.

Bruce in alaska
--
add a 2 before @

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