RR,
OK!
Do we know enough about the phase behaviour on 8.27 kHz, so we know
where we are starting from?
For ULF we would need longer symbol periods, that's sure. So it could be
interesting first to try 200s periods and a shorter message. 5
characters should be a goal, suitable for a few callsigns of active
amateur radio stations :-)
5 characters at 200s symbols, that's 28 hours and 26 minutes and 40 seconds.
I will start a transmission at that rate (this time without SL
restarting after 24 hours) and at 6 dB lower power (because of the
beeeeeeep during the working day tomorrow). 6 dB less (abt 125 mA)
should be no problem at that rate.
A first pre-test.
The cavity resonances are the frequencies seen as a horizontal (diurnal
frequency variation) line in this capture from last year:
https://dl.dropboxusercontent.com/u/19882028/VLF/dk7fc_VLF_150718_1326.jpg
73, Stefan
Am 01.05.2016 16:06, schrieb Paul Nicholson:
Amateur radio DX at ULF, that would be a result for any
dreamer wouldn't it?
You've proved that propagation will allow 24hrs at
8.27kHz, and we expect most lower frequencies will be at
least as stable - so long as we avoid the cavity resonances.
Near those frequencies, dispersion will introduce large
and variable phase delay.
So avoiding the resonances, and times of geomagnetic
disturbance, and stormy weather in Europe, and being able
to tx and rx for as long as necessary with reliable
equipment, it should be possible even with 14dB weaker signal.
The first thing to do would be to get a carrier detection
and measure that to estimate the required symbol period.
--
Paul Nicholson
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