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Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz

To: [email protected]
Subject: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz
From: DK7FC <[email protected]>
Date: Mon, 16 May 2016 22:50:04 +0200
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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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