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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: Fri, 20 May 2016 02:23:35 +0200
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A new attempt on 6470 Hz:

f = 6470.00000 Hz
Start time: 20.05.2016   00:30:02 UTC
Symbol length: 100 s
Characters: 10
CRC 16
Coding 8K19A
Duration: 20h, 53m, 20s

Antenna current: 240 mA

73, Stefan

Am 18.05.2016 21:01, schrieb DK7FC:
Hi Paul, VLF,

Hmmmm, a pity. I have been optimistic. On the other side it shows that working down there is far from trivial or normal.
Do you think the phase variations are stronger or rather unpredictable? Some time ago you said the phase changes are no problem. maybe it can be completely different on different days?
You know, Renato is updating his dreamers band spectrograms. I will run a longer carrier again soon, trying to leave a trace there. Maybe this is helpful for you to get more informations about the phase variations and their reproducability.

Markus is crazy, counting psk-ing of the carrier and pixels :-) So the capture of the decoder was a fake (?). At least not a typical decode ;-)

I calibrated the SpecLab plotter to show my antenna current directly in mA in a linear scale and show the image in png format now.
It is a good feedback for me and decoding stations to check if everything went fine so far:
Only a 3.86 kB file, ideal for regular updating on a smartphone ;-)

73, Stefan

Am 18.05.2016 20:07, schrieb Paul Nicholson:

Stefan wrote:

> f = 6470.00000 Hz
> Start time: 16.05.2016   21:00:02 UTC
> Symbol length: 100 s
> Characters: 20
> CRC 16
> Coding 8K19A

I wasn't able to decode the 18 char message.  Thanks to
Markus for the sneaky decode, I was able to reverse the
modulation to see the signal was 13.6dB in 8.8 uHz.

That puts Eb/N0 at about -6.5 dB.

Strange, I was expecting a better result because the
background noise was quite low throughout the message.

Tomorrow I'll have a closer look to try and see if
propagation is upsetting the phase.

Paul Nicholson

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