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From: "Marc H.Popek"
Subject: Re: Homebrew Microwave Interferometer
X-Newsreader: Microsoft Outlook Express 5.50.4133.2400
Date: Thu, 28 Nov 2002 17:24:10 GMT
NNTP-Posting-Date: Thu, 28 Nov 2002 17:24:10 GMT
Organization: AT&T Worldnet
James bond movie?
"Rene Tschaggelar" wrote in message
> John Jardine wrote:
> > markthomas77@Hotmail.com wrote in message
> > news:firstname.lastname@example.org...
> >>I am curious if a 10 mw cw x-band microwave radar could be used as a
> >>non contact acoustic vibration sensor? For example: if the transmitted
> >>beam from such a system were aimed at an acoustic target playing music
> >>(stereo) a few feet away and the reflected beam is combined with a
> >>sample of that beam that was sent straight into the mixer, could the
> >>acoustic micro displacements in the i.f. be phase demodulated so that
> >>the audio could be heard and understood?
> >>How could this be done exactly? Could an audio amp be connected
> >>straight onto the radars mixer pin and reproduce the audio, or would
> >>it require that the phase information be detected in an audio version
> >>of a pll and then amplified? What components would be needed exactly
> >>to connect to the radars microwave mixer pin to acheive this?
> >>I am curious if microwaves can be utilized like lasers can such as
> >>used in the laser listener systems that are well known. There is
> >>unending amounts of information on the laser systems, but none on the
> >>microwave versions. Tia.
> > A 10Ghz 'direct conversion' radar mixer like used on say, the burglar
> > detectors is pushing out 3 centimetre radiation.
> > A surface vibrating at an audio frequency would (I imagine) be moving to
> > fro in the region of a few microns.
> > I'd think that the resulting audio FM at the mixer output (including
> > reflection and path losses) would be too low to usefully recover.
> There was this case where after a certain period of time some embassy
> employees became suspicious of the window cleaners. They came a bit too
> often. They in fact did have a salty solution that was said to be radar
> reflective. I forgot the where and when of this story.
> Ing.Buero R.Tschaggelar - http://www.ibrtses.com
> & commercial newsgroups - http://www.talkto.net
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