In article ,
(Kevin Darling) wrote:

Larry Dighera wrote in message
. ..
Frankly, I didn't know that radio direction finding was employed for
aviation use before the '20s. I'd sure like to know more about this
subject.

Not ADF, of course, but DF existed from the early 1910s, and was
shortly thereafter installed on some naval vessels.

Apparently by 1914 DF was being tested on winged aircraft. The
British looped a wire from the cockpit out along the top wings, and
back via the lower wings... thus creating a loop antenna on each side
of a biplane. This allowed the pilot to easily home into his base's
radio station. ("Most Probable Position, a History of Air
Navigation")

Question: At what point in time did electronic amplification (i.e.,
vacuum tube technology) come into those systems -- or any other military
or commercial systems -- whether at the RF, audio, or any other stages?

My impression is that as of the early 1910s the transmitters would have
been either spark-gap or rotary mechanical in character, with crystal
detectors at the receiving end. When did vacuum tube amplifiers or
oscillators come into regular use in any part of these systems?