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

[rescue at sunhelp.org]

I have a less sophisticated version.  It's just two 
vertical dipoles about 2 feet apart with equal length 
coax cables to an electronic switch which alternately 
switches signal coming from the antennas to the radio.  
If the antennas equidistance from the source (same phase 
of the radio wave therefore same strength) there is no 
tone in the radio.  If one is a little ahead of the 
other, a tone is heard.  Just steer the antenna array 
for no tone and the source is broadside to the 
antennas.  The only question about those Doppler kits 
is...are they really using the Doppler effect?  (They do 
work whatever they use.)
> 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
> 
> Cheers,
> 
> Stefan
> -- 
> ========================================================================
> 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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