[Milsurplus] How VOR works

[Jim Stewart]

> Message: 8
> Date: Tue, 16 Sep 2008 16:45:17 -0400 (EDT)
> From: "Marty Reynolds" <cosmoline at aa4rm.ba-watch.org>
> Subject: [Milsurplus] VOR, 50s-style thru now
> To: milsurplus at mailman.qth.net
> Cc: Marty Reynolds <cosmoline at fracas.netboobie.org>,	Francesco Ledda
> 	<frledda at verizon.net>
> Message-ID:
> 	<1792.24.189.127.36.1221597917.squirrel at fracas.netboobie.org>
> Content-Type: text/plain;charset=iso-8859-1
> 
> 
> Francesco, hi
> 
>>
>>> I remember my father describing an early 50s ILS transmitter.  The AM
>>> modulation was achieved by motorized antennas.
>>>
> 
> That's how the the presently-used VOR works.  VOR is vhf omni range.
> 
> Antenna rotated @ 1800 rpm.  Doppler result is ~30hz 'mechanical
> modulation.'  Beginning of each cycle a 30hz separate
> carrier starts that beats the 'rotated' sig.  When beat goes thru 0 hz
> due to doppler, 'rotated-antenna' is facing you.  Since 30hz carrier
> starts @ north, via timing you know your heading
> 
> Neat.  But note antennas are now multiple electronically switched units
> & not rotated.
> 
> VOR 1st appeared about 1947.  The 'giant sombrero-looking' gizmo seen
> near airports is the antenna system.  Per N. England, TACAN used/uses
> similar df idea plus there's dme deal.

I think you're confusing Doppler VOR with
the way the traditional VOR stations worked.
The original VOR design used a physically
rotating antenna, but the phase shift was
generated electronically.

DVOR, the second generation VOR does use
doppler effect by electronically rotating
the beam around a circular array of antennas
arranged in a 13.4 meter circle.  I still
can't quite get my mind around how it works,
so here's a reference...

http://www.nordian.net/demo_files/Radio_Navigation_demo.pdf