Re: LF: Idiot's guide to receiving Ebnaut? - Tutorial part1

[Markus Vester <markusvester@aol.com>]

Hi Tony, 

downloading from the Dropbox link appeared to work fine here. Anyway I've temporarily ftp-ed Stefan's file to http://df6nm.bplaced.net/VLF/fec_tests/10111913.wav , hope that might help out. 

One minor note: Riccardo's transmission was announced and sent 0.6 milliHz above nominal. Entering a frequency offset of -14.9994 instead of -15 Hz produced a stronger and quicker decode.

All the best,
Markus 



-----Ursprüngliche Mitteilung-----
Von: Tony Baldwin <ei8jk@topmail.ie>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Sa, 15 Okt 2016 5:58 pm
Betreff: Re: LF: Idiot's guide to receiving Ebnaut? - Tutorial part1

Stefan
I can't seem to download the dropbox files, it just opens to a video playback.
Tony

On 15/10/2016 11:58, DK7FC wrote:

Hi all,

There must be some progress.
I thought it could be useful to lern how to participate in EbNaut detections by doing 2 exercises.
1: Generating wav files that contain the message
2: Configure the EbNaut decoder to read the wav file successfully.

Step 2 can be done today.
First you need to download the decoder software at http://abelian.org/ebnaut/
Then you need a wav-file containing a message. For this tutorial, you can have a wav file that was generated on my PC. It contains even 2 messages (rare!).
Download the file from: https://dl.dropboxusercontent.com/u/19882028/LF/10111913.wav
To decode a EbNaut message you have to know the start time, the symbol length, the number of characters and the Coding. These informations are given by the TX stn.
Info for message 1:

Am 11.10.2016 19:04, schrieb IZ7SLZ:

Hello LF,
Riccardo IW4DXW informs that he also will be QRV EbNaut tonight on 137485.0006 Hz
Message contains 31 characters transmitted at 0.5 s/sym, coding 8K19A, duration 14'40'' each hour starting 19.00Z  till 23.00Z .

GL.
73, Domenico iz7slz

My file contains the 19:00 UTC transmission.
Info for message 2:

Hello Group,

considering the Stefan's request, i'm pleased to test again EbNaut today on LF with a 51 characters message, 8K19A code, 0.5 s/symbol, duration 22' 40''.
QRG = 137495.000 Hz

Scheduled UT: at hour, starting from 19.00 'till 01.00 of 12-10-2016 (included). Carrier will be "on"  5 minutes before the transmissions.

Now use the EbNaut decoder and select the wav file. For the first message you can choose 31 characters, and 0.5 for the symbol period. Then press start, just for a few seconds, then stop again. You will now see some more informations: The RX freqency and the file start time. Now you can select the frequency offset, which is -15 Hz. Type that into the field.
The next thing is the timing offset. The start time is 18:54:22.340 and the message started 19:00:00. You need to know the timing offset precisely! If you don't get a decode, it is worth to vary the time offset a bit. A timing offset could of course also come from the TX stn, sometimes unknown. SpecLab causes a time offset of 4 samples. You can also see the samplerate 117.19/sec. So the timing offset is: (4S)/(117.19S/sec)+0.66sec+37sec+300sec = 337.69 seconds. Type that into the start offset field.
Now you can start the decoder and should get a decode quite quickly, depending on your PC power.

By changing just the number of characters and the frequency offset, you should receive the other message.

Fine, that was part 1 :-)
I need to get a feedback now if YOU got a successful decode or if there are problems. Depending on that feedback i would then continue with part 2.
Can someone of the 'newcomers' decode both messages?

73, Stefan