Article View: sci.electronics
Article #16068Re: measuring vehicle speed
From: Andy Warner
Date: Fri, 28 Jun 1991 17:17
Date: Fri, 28 Jun 1991 17:17
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1306 bytes
A little while ago (ie long enough that it's expired from our nntp server), someone posted an idea for bouncing radio off the road under a car and figuring out how fast you were going from testing which antenna from an array gave the best signal. Someone tell me this was a joke, please. How far is the car going to move in the time it takes for the signal to bounce back, at say 60MPH .. Well my rough calculations say about .. 2nS (assuming a 50cm path, s = 3x10^8 m/sec - rough, but the right order of magnitude). So how far does your average 60MPH Subaru move in 2nS ? Roughly 0.000006 cm. I think the engineering tolerances might be a little tight here.. Now, I could have the wrong end of the stick here, but I don't think so. -- andyw. (W0/G1XRL) andyw@aspen.cray.com Andy Warner, Cray Research, Inc. (612) 683-5835
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arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!spool.mu.edu!cs.umn.edu!uc!shamash!timbuk!andywShow Full Headers
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!spool.mu.edu!cs.umn.edu!uc!shamash!timbuk!andyw From: andyw@aspen32.cray.com (Andy Warner) Newsgroups: sci.electronics Subject: Re: measuring vehicle speed Message-ID: <110139.19717@timbuk.cray.com> Date: 28 Jun 91 17:17:17 GMT Followup-To: sci.electronics Distribution: na Organization: Cray Research, Inc (People who make computers out of ECL). Lines: 27