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Re: VLF: EbNaut 3 character attempt to VK7

To: [email protected]
Subject: Re: VLF: EbNaut 3 character attempt to VK7
From: DK7FC <[email protected]>
Date: Wed, 26 Sep 2018 09:08:50 +0200
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.de; s=2017; t=1537945736; bh=pbOe1DCWMUE4EkaDKjuXw0r783vPCBYq1y1ZRK50JJ4=; h=Date:From:To:Subject:From; b=oI0fmdebEaimQBWss2eVKeG/XuYH0L9mbi9SbCDPVPGOI4Ct++ALURU7vJoRGatu2 fUFjNtiAWwDcJBBYLple/nTP9JIEAuBI353PMCwFveGWcKSOKngqAC/1gcpP9at1Pr fzlBp1Z4i1IIFdx5jkzP8TdCeiy7OB3L7Se1Heomln2tyUs9btGyXMvdDBBjORh2aT uYrPXzO8notpZa5iymAFNPj+nf3fX3dFm2q9VIWQ+Bb6wGoA9Rga4k27kWYKJYy1dS Rh7bEQCebyNxI7Yl7d0DgEVE+QUctLfo5oSfZPIvtU+TqpN6K7wgPa9WWvuS3Q2Uzg Kz5vFQHSJxADQ==
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Here is an update on the ongoing experiment between Edgar and me, trying to pass a 3 character EbNaut message over to VK7 on 17.4701 kHz.

Since the 21st September i'm transmitting the same message with identical parameters, one starts at 16:30 UTC, the other one at 19:30 UTC.
After some days it showed that the first time slot does not develop positively (2 days = +3 dB, 4 days = +6 dB....). The second message was more promising. After 3 days stacked it got up to 9.71 dB SNR. Best result so far:
rank 2673527 ber 4.5833e-01 Eb/N0 -5.3 M -6.947182617e+02 ph 77 150,180,150,180
But this is not really a valid decode because you only get it when knowing the message before and searching explicitely for it.
Yesterday i got the 4th file, today the 5th.
Adding the 4th and 5th file to the stack unfortunately lowers the SNR again.

What now?
There is something to try:
These days the sunset happens about 2 minutes per day earlier. I want to try if it helps to start the transmission 2 minutes earlier per day. Of course this must be considered / compensated when building the stack.
So now i'm continuing to transmit the same messages but the start times will be:
26th: 16:28 and 19:28 UTC
27th: 16:26 and 19:26 UTC
28th: 16:24 and 19:24 UTC


and so on...

We have not been to far away from a valid decode, so let's hope this will help.

Comments or ideas?

73, Stefan


Am 20.09.2018 21:12, schrieb DK7FC:
Correction: Same parameters as used for the first message, i.e. both messages use

f = 17470.1000 Hz
Start time: 20.SEP.2018  19:30:00 UTC & 16:30:00 UTC (daily)
Symbol period: 10 s
Characters: 3
CRC bits: 19
Coding 16K21A
Antenna current: 1.2 A


73, Stefan


Am 20.09.2018 21:02, schrieb DK7FC:
VLF,

In addition to the message below, which has been transmitted 3 times already, i will start to transmit the same message into a later time slot, also using different parameters:

f = 17470.1000 Hz
Start time: 20.SEP.2018  19:30:00 UTC (daily)
Symbol period: 10 s
Characters: 3
CRC bits: 16
Coding 16K21A
Duration: 02:24 [hh:mm]
Antenna current: 1.2 A

73, Stefan

Am 17.09.2018 16:14, schrieb DK7FC:
Edgar, VLF,

After evaluating the latest 4 days of carrier transmissions it shows that the path from DL to VK7 is quite unstable, i.e. the phase is very dynamic.  When applying different frequency offsets, it seems that the best start time for a message attempt is 16:30 UTC these days. The SNR then peaks when applying a -40 uHz offset, attached. Something between 2...3 hours seems to be best. Currently 2 hours seem to give better results but 3 hours would be less dynamic.
Based on this data i'm trying:

f = 17470.1000 Hz
Start time: 17.SEP.2018  16:30:00 UTC (daily)
Symbol period: 10 s
Characters: 3
CRC bits: 19
Coding 16K21A
Duration: 02:32 [hh:mm]
Antenna current: 1.2 A


73, Stefan
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