> when back in the mid 90's the initial request for a longwave amateur
> segment (what later turned out to be 137kHz) was discussed, one of the
> big telecom "bobo's" stated that they saw no harm that amateurs would
> transmit there with max. 1 W EIRP as with that power one wouldn't be
> able to get any further than the other end of the town.
> It turned out a bit different, unless you see the world as one big town ;-)
Rik, after some theoretical estimations done i am absolutely shure
QRSS communications at few 100s km (may be more) is posible on 9 kHz.
There is lot of problems on TX side but them to be solvable. Main problem
is high voltage on the TX ANT. I expect 100 - 200 kV is reachable with
some 'tricks' wellknown for power ingeneers. For example one should avoid
free end of a wire with such a voltage. On should use 'protecting rings'
on the ends. With voltage abt 100 kV seems to be posible use not too high
antenna. Seems 20-30 m high well top loaded marconi designed specially for
high voltage is adequate. Remember effective height of 60m kite antenna
used in DK8KW experiment was 30m (if wire was absolutelly vertical, does
it was?). With not too high voltage and not too large ANT capacity 4.5 km
was reached. Another key problem is noise level on this freq. Now we see
huge discrepancy on the noise level got from different sourses. What is
the real noise level is not obvious now. Can it be much lower time to
time? Experements to be usefull. Look at DK8KW web side where 4.5 km
experiment is described. Waterfall background is too smooth. Where
spherics are? This is why i expect RX sensetivity was not as
high as posible. One should remember 4.5 km is begining of the wave zone
on 9 kHz. At distanses more then 4.5 km field decreases not too fast with
distance. Another critical distance is abt 100 km where 'waveguide'
propagation starts. At such distances one shold increase TX ANT voltage
only in 3 times to reach distance 10 times more. Anyway Stefan's
experiment will be very intesesting. And i hope it will be not the last
experiment.
Regards,
Alexander/RA9MB
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