From: John Larkin
Subject: Re: Radar Microphone?
Date: Tue, 07 Jan 2003 10:22:55 -0800
Organization: Posted via Supernews, http://www.supernews.com
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On 7 Jan 2003 03:40:35 -0800, MarkThomas77@Hotmail.com
>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?
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.