[rescue] Radio DF equipment (was Ham radio license question)

Stefan Hames rescue at sunhelp.org
Sat Jun 9 10:02:23 CDT 2001

At 14:29 -0400 6/8/01, James Sharp wrote:
>I picked up the Doppler DF-1 kit from Ramsey Electronics
>(http://www.ramseyelectronics.com).  It was about $140, IIRC.  Took me
>about 2 days to build and it seems to work fairly well.  All you need is
>an outboard receiver with an audio out jack.
>It electrically rotates a set of 4 antennas to induce a dopper shift in
>the signal which shows up as a tone in the receiver audio, which it then
>decodes for relative bearing.
>I'm going to hang a PIC chip off of it for digital out, then mix that in
>with input from a GPS and a compass.  I'll then wash it through some
>computerized trig functions for triangulation...take a few spaced out
>samples, and suddenly you have an absolute lat/long position that can be
>presented to you on a display.

I'd be very interested in the details of your set-up if you get that 
working.  I have a similar application that involves tracking birds 
in the wild that are carrying small telemetry transmitters.  What's 
prevented me from trying to work it out so far is the lack of gain 
from the (I'm assuming) whip antennas.  The birds can only carry 
_tiny_  x-mitters.  What I've done so far is do real-time 
triangulation using portable 5-element Yagis (one hand-held, the 
other mounted to the roof of a car - I get some really odd looks).  I 
use some published SAS code to give me estimated positions and their 
associated error polygons.  I'd be glad to send you the code; it's 
only a few lines but should be easy to port, and might be easier than 
reinventing this particular wheel


Stefan Hames
Ecology and Evolutionary Biology
E221 Corson Hall
Cornell University, Ithaca, NY 14853-2701
Phone: 607-273-4915 (home)
        607-254-2496 (lab)
        607-254-4262 (campus)
        607-255-8088 (fax)
<mailto: rsh5 at cornell.edu>

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