Long DX !

[Andre' Kesteloot]

 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
pieced
together all the loading coils they could find and managed to get the
small
antenna at Haiku tuned to 6250 hertz. At this frequency the power
radiated
could not have been more than a very few milliwatts. I observed the
signal
at Cambridge (Massachusetts, USA) with our photographic technique,
using
triggering pulses at a submultiple frequency, so that a cycle or two
stood
still on an oscilloscope screen and the photographic record (which
plotted
the oscilloscope picture against time of day) appeared as black and
white
stripes. During the night the signal was marvelously clear but at
sunrise
it declined so rapidly that at first I thought that the transmitter
had
been turned off. This was because that frequency of the signal came
close
to or below the cut—off frequency in the waveguide-like space between
the
earth and the lowest ionized layer. The height of the layer dropped
suddenly when the first rays of sunlight reached it in the morning,
and the
attenuation of the signal increased rapidly. This and one or two other

experiments between six and ten kilohertz convinced us that reliable
long—distance operation was not to be expected at all hours at a
frequency
much below ten kilohertz."

Date?  January 1946.

The "small antenna at Haiku"  was a 300 ft vertical! These experiments
led
to the development of Omega, 10.2, 11.666, and 13.3 kHz.

Walter G3JKV