Long DX !
Wed, 08 Mar 2000 10:23:17 -0500
I found [this] in the memoirs of Dr Jack Pierce (MIT, USA) who had a
hand in the design of Omega and Loran-C :
"On the occasion I found most interesting, the boys in Hawaii had
together all the loading coils they could find and managed to get the
antenna at Haiku tuned to 6250 hertz. At this frequency the power
could not have been more than a very few milliwatts. I observed the
at Cambridge (Massachusetts, USA) with our photographic technique,
triggering pulses at a submultiple frequency, so that a cycle or two
still on an oscilloscope screen and the photographic record (which
the oscilloscope picture against time of day) appeared as black and
stripes. During the night the signal was marvelously clear but at
it declined so rapidly that at first I thought that the transmitter
been turned off. This was because that frequency of the signal came
to or below the cutóoff frequency in the waveguide-like space between
earth and the lowest ionized layer. The height of the layer dropped
suddenly when the first rays of sunlight reached it in the morning,
attenuation of the signal increased rapidly. This and one or two other
experiments between six and ten kilohertz convinced us that reliable
longódistance operation was not to be expected at all hours at a
much below ten kilohertz."
Date? January 1946.
The "small antenna at Haiku" was a 300 ft vertical! These experiments
to the development of Omega, 10.2, 11.666, and 13.3 kHz.