EMRFD Message Archive 3359

Message Date From Subject
3359 2009-07-29 15:27:11 Jim Miller supersonic mic?
Anyone know of inexpensive microphones which might cover 10khz to 40khz? I'd
like to make a heterodyning audio receiver and am looking for a sensor.

tnx
jtm


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3360 2009-07-29 15:58:49 w4zcb Re: supersonic mic?
Anyone know of inexpensive microphones which might cover 10khz to
40khz? I'd
like to make a heterodyning audio receiver and am looking for a
sensor.

tnx
jtm

Try an electret. They're flat as a pancake 20 Hz to 20 KHz, haven't
tried, but suspect they're not all that far down at 40 KHz. $0.50 each
or 3 for a buck at radio Shack.

W4ZCB
3361 2009-07-29 16:06:59 Don AE5K Re: supersonic mic?
Jim Miller wrote:
> Anyone know of inexpensive microphones which might cover 10khz to 40khz? I'd
> like to make a heterodyning audio receiver and am looking for a sensor.
>
> tnx
> jtm

Jim,

You might try Phil W0XI ... see this:
http://ozarkcon.com/w0xi/w0xi.htm

His present email address is:
aldenmcduffie@sunflower.com

He presented at OzarkCon 2009 a nice showing of what I think you are
seeking and has some handouts that he might send you. He has done
extensive work and study in this area.

73,
Don AE5K
3362 2009-07-29 16:09:26 Don Hackler Re: supersonic mic?
The transducers used in old ultrasonic buglar alarm units might work.
Also the piezo transducers used in electronic "tape" measures.


Jim Miller wrote:
> Anyone know of inexpensive microphones which might cover 10khz to 40khz? I'd
> like to make a heterodyning audio receiver and am looking for a sensor.
>
> tnx
> jtm
>
>
>
>
3363 2009-07-29 16:11:25 Jim Miller Re: supersonic mic?
thanks for the pointer. i've been googling around and it seems everything is
characterized to 20khz. i think i'll go with your suggestion and just try
some. i need to build up the LO, mixer and some preamps.

tnx
jtm


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3364 2009-07-29 19:43:39 Andy Re: supersonic mic?
> Try an electret. They're flat as a pancake 20 Hz to 20 KHz, haven't
> tried, but suspect they're not all that far down at 40 KHz.

Condenser mics are not uniformly flat. They all have a diaphragm
(mechanical) resonance somewhere up there, and that probably limits
their response. Some of them exhibit a broad peak around 5-12 kHz and
a rolloff above. Others are nearly ruler flat to 50+ kHz. Years ago
I read a few articles about using those for ultrasonic probing. The
particular mics they used were expen$ive (lab standard variety).

I don't know for sure, but I'd expect the alarm ultrasonic transducers
might be rather narrowband.

Andy
3368 2009-07-29 23:22:53 John Kolb Re: supersonic mic?
I've been using the Transsound TS-60A to plot tweeter responses above 30 kHz.
I pick up a strong signal about 45 kHz from what's probably an ultrasonic alarm
somewhere in the building so the mic response goes way up there.

http://jlielectronics.com/transsound/electrets/index.htm?Submit2=Electrets

http://jlielectronics.com/transsound/electrets/ts-60a.htm

Less than 50 cents.

John

At 03:26 PM 7/29/2009, you wrote:
>Anyone know of inexpensive microphones which might cover 10khz to 40khz? I'd
>like to make a heterodyning audio receiver and am looking for a sensor.
>
>tnx
>jtm
>
>
>[Non-text portions of this message have been removed]
>
>
>
>------------------------------------
>
>Yahoo! Groups Links
>
>
>
3369 2009-07-30 04:10:46 w4zcb Re: supersonic mic?
I've been using the Transsound TS-60A to plot tweeter responses above
30 kHz.
I pick up a strong signal about 45 kHz from what's probably an
ultrasonic alarm
somewhere in the building so the mic response goes way up there.

http://jlielectronics.com/transsound/electrets/index.htm?Submit2=Electrets

http://jlielectronics.com/transsound/electrets/ts-60a.htm

Less than 50 cents.

John

Makes one wonder. Other than bragging rights that you have money to
throw away, why anyone would pay $200 for a Heil mike.

I get rave reviews on my TX audio, with an electret boom mike which
complete with headset cost $6 at Best Buy. Ah! Marketing!

W4ZCB
3552 2009-09-17 08:26:26 opdecamr Re: supersonic mic?
Hi,

Look for Bat detectors.
A nice place to start is:

http://bertrik.sikken.nl/bat/detuning.htm

Friendly greetings,
Michel ON4DCP


3553 2009-09-17 11:16:46 michael taylor Re: supersonic mic?
3554 2009-09-18 06:19:33 Dave Re: supersonic mic?
3555 2009-09-18 07:36:59 Glen Leinweber supersonic mic?
Commonly available piezo-electric transducers, used
in motion detectors are quite narrow-band devices,
with an equivalent circuit similar to a crystal. A bat-
detector would benefit from a wider response (30Khz
to 70KHz).
You can widen the peak response of a piezo
transducter by adding a parallel inductor. For example,
a 40 Khz. transducer measured characteristic, using
the nomenclature of crystal equivalent circuit:

Lm = 92.1 millihenry
Cm = 175.38 picofarad
Rm = 634 ohms
Cp or Co = 1300 picofarads

Maximum TRANSMITTED acoustic responsivity is at
39.8 Khz., close to series resonance @ 39.6 Khz..
Parallel resonance is at 42.36 Khz.

By resonating out the parallel capacitance of 1300 pf,
receiver bandwidth can be widened - useful in a bat
detector. The parallel inductor required is 12.4 millihenry.
Bandwidth of a bare transducer can be extended roughly
ten times this way. A loading resistor of 5500 ohms helps
to flatten the frequency response.
Hope you find this example case useful,
-Glen
3556 2009-09-18 18:42:58 John Kolb Re: supersonic mic?
For audio and ultrasonic, we have had good results using the
TS-60 microphone from JLI Electronics. The WM-61A from Digi-Key
should give similiar results. Cheap electret element microphones
are seldom specified above 20 kHz, but if flat up to 20kHz have
useful response well above that.

John

http://jlielectronics.com/transsound/electrets/index.htm?Submit2=Electrets


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