[Milsurplus] Naval Aviation Navigation

[Ed Zeranski]

Mac, the antenna wouldn't have to rotate and produce
the azmuth information if all you wanted is DME.   On
a VORTAC the VOR antenna rotates a heart-shaped
pattern which makes the azmuth info.

	Yep. In the base TACAN sets I worked on the antenna was stationary but the
parasitic elements spun. The triggers for the main and aux bursts were
generated by iron slugs in an aluminum plate that rotated with the 900 rpm
spinning parasitic drum. As the little iron bits passed through coils they
generated the triggers. Distance interrogation came from the aircraft and
that only happens when the flyer turns on the DME part of his set. We had an
old ARN-21 mounted in our truck as a monitor. Civilian aircraft can monitor
the mil sites and the mil TACANS were on the aircharts. The civilian use put
an FAA AZ accuracy requirement on land based mil TACANS.

EdZ