Hi Paul, VLF,
A spontaneous impulse/idea:
Let's be optimistic and try the long message in 100s symbols. The
announcement happens a few minutes before the start of the transmission
:-)
f = 6470.00000 Hz
Start time: 16.05.2016 21:00:02 UTC
Symbol length: 100 s
Characters: 20
CRC 16
Coding 8K19A
Duration: 34h, 13m, 20s
Antenna current: 240 mA
16K25A and 200s, that's a job for the lower frequencies. I have to send
the mail now, otherwise it comes to late ;-)
73, Stefan
Am 16.05.2016 07:38, schrieb Paul Nicholson:
Stefan wrote:
> would you think that going from 100s to 200s will improve
> things by about 3 dB?
Yes, or better: keeping to 100s and going to a 16K mode instead
of 8K for an increase of coding gain.
> How long do you record the VLF soundcard stream?
About 65 months at the moment.
> Would it be possible, for example, to transmit a 1 week long
> message, without an announcement before the start?
Yes, in principle. The longer the message the more chance of
a battery problem or sheep knocking down one of the antennas,
or thunderstorm or power cut, or one of the cats sleeping on
top of the GPS antenna.
But with a long message, an interruption of a few hours is
not a disaster. After a power cut, my rx will restart with
the same reference phase and continue recording so there will
be a gap but no loss of phase.
We may have to put this to use when we reach ULF.
Un-announced is ok because of the continuous recording but better
to announce if possible so that I know not to do maintenance
(or tests with kites! Will be playing with the Power Sled 24).
--
Paul Nicholson
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