Radar Microphone?

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Jan 7, 2003, 6:40:35 AM1/7/03
I have one of those cheap Ramsey personal speed radars and was playing
around with it pointing it at a fan and watching the speed display
numbers rapidly change back and forth, when it occurred to me to
connect a pair of headphones to the radars earphone output to see what
I would hear. I could hear the fans blades rotating! I then set the
unit down on a table and started trying to "hear" different objects.

I clanked some keys together, compressed and then rapidly released a
pair of tweezers, etc. I was able to hear the actual audio from these
objects, but the audio quality was absolutely terrible. There was too
much bass in the audio and the audio was terribly distorted.

My question is this: what could I connect to the radars earphone
output that would reduce the exaggerated bass frequencies, and also
clean up the audios tremendous distortion?

Don Pearce

Jan 7, 2003, 7:10:17 AM1/7/03
On 7 Jan 2003 03:40:35 -0800, MarkTh...@Hotmail.com
(markth...@Hotmail.com) wrote:

These Doppler RADAR devices give an output signal that is identical
whether the target is coming or going. This means that the output, in
audio terms, is full-wave rectified, and as you say very distorted.
There is no way round this that I can think of. The bass heaviness is
due to the integration effect of a frequency modulated signal going
through a phase detector. A 6dB per octave filter will take care of
this. You will never get good results, though, because the very
considerable phase noise of the oscillator is converted down into the
audio band by the detector.


Telecommunications consultant

John Larkin

Jan 7, 2003, 1:22:55 PM1/7/03
On 7 Jan 2003 03:40:35 -0800, MarkTh...@Hotmail.com
(markth...@Hotmail.com) wrote:

This is a gunn diode transmitter and a diode-mixer receiver. The diode
output is roughly abs(cos(distance)) or something horrible like that,
which is nonlinear as hell except in the occasional small sweet spot
on the sides of the curve. But at the diode itself, the 'frequency
response' (versus displacement) should be flat, at least if the diode
is properly loaded.

Tuning forks are sometimes used to calibrate police radars.



Jan 7, 2003, 3:20:11 PM1/7/03
If a gunnplexer had 2 mixer pins, one pin providing the doppler shift
fm i.f. information, and the other pin having a direction sensing
capability by providing the phase difference i.f. from between both
mixer pins, would that make a difference as far as removing or
reducing the distortion to a noticible degree? Could the phase
information from pin 2 be demodulated and amplified in some way so
that it would provide cleaner audio?

It would seem the answer is no. Because the audio from either mixer
pin is still distorted by phase noise from the oscillator that has
been down converted into the audio frequency band. Right? Oh well,
thought I would ask anyway. Thanks.

Don Pearce <don...@pearce.uk.com> wrote in message news:<cmgl1v454m2ind66e...@4ax.com>...

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