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From: prem@crackle.amd.com (Prem Sobel)
Newsgroups: sci.electronics
Subject: Re: direction finder
Message-ID: <25815@amdcad.AMD.COM>
Date: 1 Jun 89 14:40:11 GMT
References: <11269@megaron.arizona.edu>
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Reply-To: prem@crackle.amd.com (Prem Sobel)
Organization: Advanced Micro Devices, Inc. Sunnyvale CA
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In article <11269@megaron.arizona.edu> wendt@arizona.edu (Alan Lee Wendt) writes:
>I'd like to build a direction finder that my wife (who's blind)
>can use to find the house.  Something with a range of 2 miles or
>so, that could be left on all the time at the house and a small
>battery-operated hand buzzer that would stop buzzing when lined
>up with the direction of the house.
>
>Help me get my wife her instrument license.  What frequencies
>are available for this kind of use?  Anybody have any designs
>for bits of this?

Since city blocks are not radial, it might be useful for there to also
be an audible distance measurement, but that is VERY expensive. For
direction a system similar to the aircraft VOR system might be useful
(again unfortunately very expensive), which sends an omnidirectional
radio pulse out at the same time it uses a phased array to sweep a
beam around at a known rate. The receiver measure the time between the
omnnidirectional and swept beam to give angle to transmitter.

If power levels are below a certain level (100 milliwatts I believe)
or the signal is on on certain allowable experimental frequencies
(above VHF) then no license is needed.