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?
(markthoma...@Hotmail.com) wrote: >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?
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.
(markthoma...@Hotmail.com) wrote: >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.
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.
> >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?
> 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.
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