Mike Marron wrote:
(Walt BJ) wrote:

(Snip)

Anyone ever flown an NDB approach via an old fashioned
loop antenna? (For the readers unfamiliar with the terminology,
NDB means "Non Directional Beacon" which is usually a
low-freq signal emanating from a commercial AM radio station
or transmitter on the ground.)

I don't remember that we ever hand-cranked the loop, but I do remember turning
the loop back and forth from the cockpit looking for the null, which represented
the NDB. Isn't it funny what age does to the memory.....I remember doing it but
can't recall why or how it was supposed to work. BTW, I'm referring to a Troop
Carrier gooneybird, by way of type aircraft, and my time frame was from '43 to
the end of the war.


On newer aircraft, the pilot tunes in an NDB station simply by
turning a dial in the cockpit, but many older (WW2-era) aircraft
required the pilot to crank a lever that physically rotated a loop
antenna mounted on top of, or beneath the fuselage so as to
pick up the NDB or radio station on the ground.

The Japanese planes that attacked Pearl Harbor homed in on
their targets via loop antennas tuned a commercial radio station
(imagine listening to peaceful Hawaiian music while plummeting
straight down at the USS Arizona with a 1,760-pound armor-piercing
bomb!)

Hey, I just remembered how some of it worked. When you lined upthe plane of
your loop with the broadcasting station, signal reception disappeared (hence,
flying the null). You got your best signal reception when the opening in the
loop was perpendicular to the station it was tuned to. Flying the null in
itself didn't tell you if you were inbound or outbound, just that it was either
right ahead of you or right behind you. Seems to me that there was some sort of
turning maneuver that was used to watch the null movement that told us if we
were approaching the station or had just passed it. I can't recall the
explanation for how that worked.....it's been too many years, I guess.

George Z.