[Milsurplus] VOR, 50s-style thru now

[Marty Reynolds]

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.

  Marty

Caution: pilot-in-command must NOT dwell on this!  Right Hank?