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

[rescue at sunhelp.org]

I was just wondering if it did actually use the Doppler 
effect or was just measuring phase of the incoming wave 
at two antennas like the two antenna design that I have. 
 Not really knowing how they are supposed to work (as 
opposed to how they claim to work) and from the 
description given, it just did not look like Doppler to 
me, just measuring phase difference between the antennas. 
 Obviously there has to be some heavy calculations to 
determine the sum and difference frequencies of the 
received signal due to the rotation of the virtual 
antenna to determine the direction of the source.  
Something that an IPX might not be able to do (to get 
this back on track).  

> They do use the dopper effect.  By electrically switching between the
> antennas fast enough, the antenna system becomes a single virtual antenna
> that is being swung about the circumference of a circle that can be
> calculated by the switching frequency & the reception frequency.
> 
> Picture someone swinging a noise maker at the end of the rope.  As the
> noisemaker approaches you on the swing, doppler shift increases...it
> decreases as the noisemaker swings away.  Same concept, except the
> noisemaker is stationary & the receiving point is moving.
> 
> 
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