Re: [PSUBS-MAILIST] Desert Star Sport

["Jens Laland" <laland@artematrix.org>]

Jon

Here is a quote from my communication with an electrical engineer (sonar
technology), who started his career back in 1947, and worked all his life
designing and building sonar transducers and related equipment for the US
Navy:

"Keep in mind that for transmitting (as a projector) you have to operate
at the resonant frequency of the ceramic element. Otherwise, the
efficiency (off resonance) is very low. But for hydrophone use, you
usually use the element below its resonance where the receiving response
is flat."

Hence, it would therefore be interesting to compare the frequency
responses of two general-purpose low-cost hydrophones, namely David
Bartsch's HBH-2 and Sensor Technology's SQ26, ref(s)

http://www.psubs.org/projects/common/scripts/display/bigpic.cgi/projects/1234567815/passivesonar/1265151470.jpg

ftp://ftp.artematrix.org/sonar/hydrophone/SQ26/SQ26-05_Frequency_Response.pdf

Also, here is a short, one-page description of the SQ26 hydrophone, ref

ftp://ftp.artematrix.org/sonar/hydrophone/SQ26/SQ26.pdf

Best regards,
Jens Laland


** Jens,
**
** I can't speak to that.  We'll need to hear from Al, Lea, or someone else
** more versed in electronics then I.
** I was under assumption of the opposite and that "resonant frequency"
** meant exactly what it implied, regardless of transmit or receive.  Like
** other similar electronics, the efficiency of the unit varies as
** frequency changes (you can see this in the Reson specifications) so I
** suppose it's possible that a 63khz unit could work at half the
** frequency.  The question would be how effective it is at half the
** resonance.  It sounds like you are describing a comparison of using a
** half-wave or quarter-wave antenna for a radio transceiver which of
** course works, but I don't know if that concept translates to a change of
** frequency for a given element resonance.
**
** Jon
**
**
** Jens Laland wrote:
**> Correct me if I'm wrong, but I have been told that a transducer should
**> always be operated (at least in listening mode) below it's resonance
**> frequency.
**>
**> ** the real question is does DS or their suppliers have 32khz
**> transducers
**>
**> If what I'm told is still valid, then a transducer having it's resonance
**> frequency at, let say 63 kHz, should be excellent for communication at
**> around 32 kHz...
**>
**> and that is why I recently bought a couple of these piezoelectric
**> ceramic
**> cylinders, ref
**>
**> http://www.steminc.com/piezo/SMC26H25T175W62K.asp
**>
**> Best regards,
**> Jens laland
**>





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