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Re: LF: Re: EbNaut test transmission

To: [email protected]
Subject: Re: LF: Re: EbNaut test transmission
From: Markus Vester <[email protected]>
Date: Tue, 17 Nov 2015 12:51:46 -0500
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Andy,
 
getting even better... 56/704 symbol errors and 11.2 dB Eb/N0 for the 16:30 message.
 
I'm sure that Domenico will be able to pick up the signal in South Italy. Would anyone in TA-land want to attempt a decode tonight?
 
For receiving with SpecLab, you could use the opds-spectrum-export and IFFT method, as described in my post to blacksheep on Sep 27th (I could repost if required).
 
73, Markus


-----Ursprüngliche Mitteilung-----
Von: Markus Vester <[email protected]>
An: rsgb_lf_group <[email protected]>; rsgb_lf_group <[email protected]>
Verschickt: Di, 17 Nov 2015 5:59 pm
Betreff: Re: LF: Re: EbNaut test transmission

Well done Andy!
 
This decode was from a message before the NTP adjust. Your transmit frequency looks stable and accurate.
 
I have temporarily moved the opds SpecLab instance to your frequency, and inverse Fourier transformed a saved opds spectrum data file.
 
Domenico and I have successfully tried speeds up to 0.1 second symbols, with no additional tweaking after we'd once got the time offset right.
 
Best 73,
Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von: Andy Talbot <[email protected]>
An: rsgb_lf_group <[email protected]>; rsgb_lf_group <[email protected]>
Verschickt: Di, 17 Nov 2015 5:26 pm
Betreff: LF: Re: EbNaut test transmission

Its still going.
At 1611z I ran rsNTP and it made a PC clock adjustment of 0.4 seconds, which with the 0.5s symbols used for this transmission will glitch slightly .

Pleased to note that a local recording I made using the  new LF Receiver hardware and my own software to generate a .WAV file compatible with Spectrum Lab's did generate a valid decode. Recorded at fs = 31.25Hz  That was before the PC time had been corrected and I had to do a fair bit of shuffling with the Start Offset value to get a decode.   Values from 0.45s to 0.85s worked - much of that presumably due to the PC time offset in the transmission.   But once a value in that range had been entered, zero decode errors - which is what one would expect of a very strong local copy !

It does appear that using EbNaut with rates much faster that 2S/s could end up very fraught with timing offsets.  Fortunately, weak signalling with longer symbols of several seconds will have less of a problem with timing offsets.

Andy  G4JNT


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