Re: VLF: sub-9-kHz TA E>W ?

[Markus Vester <markusvester@aol.com>]

Hi Stefan,

nice decodes in Amberg again, this time with Eb/N0 = 19.5 dB for the nighttime single character message, and 3.8 dB for 12 characters during the day. Adjusting by 10.5 dB for message length and duration, nighttime SNR was still 5.2 dB better than daytime, despite much higher noise level. This is clearly due to the midday skywave cancellation effect which is apparent on the DL0AO grabber: After 8 UT the PSK-noise-strip was briefly visible on vlf12, but faded quickly into the background. After decoding the message, I engaged unspreading after 13:45, allowing us to watch the carrier build up again during the rest of the afternoon. If you decide to repeat the daytime show tomorrow, we'll hopefully be able to produce a complete amplitude and phase plot across noon.

Best 73,
Markus


-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 16. Feb 2018 23:39
Betreff: Re: VLF: sub-9-kHz TA E>W ?

VLF,

The next transmission (1 char TA attempt) is now running again. The PA and system is back in normal operation.

Tomorrow, i'm transmitting a message in daytime, just for fun. Not every tranmission need to become a new record :-)

f = 8270.1000 Hz
Start time: 17.FEB.2018  08:00:00 UTC
Symbol period: 32 s
Characters: 12
CRC bits: 16
Coding 8K19A
Duration: 07:32:16 [hh:mm:ss]
Antenna current: 700 mA

73, Stefan




Am 15.02.2018 23:24, schrieb DK7FC:

VLF,

No transmission tonite again. Something is not working with the PA :-/ I replaced a FET that died due to heat. Now the working point seems to cause a thermal drifting towards bad efficiency. The DC offset seems to be to high and there is no thermal feedback diode on the heat sink... I'll investigate...

73, Stefan

Am 15.02.2018 12:27, schrieb DK7FC:

VLF,

Last night (14th/15Th) my transmission failed. I still don't know the reason but will check it later. I hope to be on air again this night...

73, Stefan

Am 13.02.2018 21:25, schrieb DK7FC:

Thanks Markus,

29 dB S/N, quite a good result on your side :-)
>From the tree i received the message with 0 symbol errors even.
I got the file from Jay. It looks we will need a long time :-) But tomorrow the tendency may be a bit more clear (even if not clear it will be clear :-) ). Let's hope the stacked file will show better than -10 dB tomorrow...

73, Stefan

Am 13.02.2018 21:16, schrieb Markus Vester:

Hi Stefan,

excellent "local" decode from the cardioid in Amberg:

list rank 0
reference phase 180,180,180,180
carrier S/N 29.02 dB in 39.1 uHz, -15.06 dB in 1Hz, -49.04 dB in 2.5kHz
carrier Es/N0 -0.01 dB
carrier Eb/N0 21.46 dB
info bit period 4491.23 seconds
symbol error rate 81/800 = 10.125 %
Es/N0 from symbol errors -0.9 dB
Eb/N0 from symbol errors 20.6 dB
Shannon capacity 112.3 bits/hour
Shannon efficiency 0.7 %
symbols file 8k27W_02130025-symbols.csv
elapsed 34 seconds

Good luck to you and Jay, and anyone else who might want to take the challenge.

73, Markus



-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di, 13. Feb 2018 0:01
Betreff: Re: VLF: sub-9-kHz TA E>W ?

VLF,

OK, Jay responded to me personally. We will take the challenge.

The first transmission is already running:

f = 8270.1000 Hz
Start time: 12.FEB.2018  22:32:00 UTC (daily)
Symbol period: 32 s
Characters: 1
CRC bits: 24
Coding 16K21A
Duration: 07:06:40 [hh:mm:ss]
Antenna current: 700 mA

Reports welcome :-)

73, Stefan



Am 12.02.2018 15:00, schrieb DK7FC:

Jay,

You are the one! The one on the other side of the pond who could manage to get a decode of a message trasnmitted on 8270 Hz, transatlantic east to west. This has not been done so far.

Are you interested and ready? You would need to run your PC for a few days without restarting SpecLab or doing changes in that SpecLab instance. You could provide the txt files so i can have a look and see if the stacked Eb/N0 is building up, confirming that it makes sense to continue to transmit.

I have no idea if this will work with my small signal.

Do we want to try? I would start transmitting this evening already if you say GO!

73, Stefan