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Re: LF: Coherent BPSK on LF using EbNaut

from [Andy Talbot] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: Coherent BPSK on LF using EbNaut
From: Andy Talbot <[email protected]>
Date: Fri, 25 Sep 2015 12:23:40 +0100
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EbAnut is a new one here - I hadn't heard of it.   After Googling I found the page and read up / downloaded the software.   Unfortunately, I see it is not standalone, and requires Spectrum lab to act as the audio "front end" to take in the Received audio, downconvert to a baseband I/Q and store that as a .WAV file.   So downloaded Spectrum lab and tying to wade through how to use that.

Could you perhaps give a short cut simple explanation of how to set up Spectrum lab to do that - it looks to be a very complex bit of software to drive.
the EbNaut Tx and Rx programmes, in contrast, look very simple to use and it would be goo dto get more people using sensitive coherent signalling such as this.

Some years ago I proposed GPS / UTC seconds locked coherent signalling on LF, but didn't have the expertise to write the software - and certainly not to implement strong FEC !

Andy  G4JNT


On 23 September 2015 at 01:04, IZ7SLZ <[email protected]> wrote:
Hello LF,

I am pleased to report a successful "Coherent BPSK" QSO between DF6NM and IZ7SLZ on LF using EbNaut program of Paul Nicholson.
QSO took place in the night between Friday 2015-09-18 and Saturday 2015-09-19 .

I think it was the first time that anyone tried this on 137 kHz !

Frequencies used were 137510.00 Hz (DF6NM) and 137502.12 (IZ7SLZ).

We exchange messages of 16 characters in coherent BPSK with UT synchronous symbols, using a symbol period of 1 second and 8K19A scheme coding.

Software used were the Windows' versions of EbNaut-TX and EbNaut-RX (tnx to P. Nicholson: your software is working without problems!).
Also Spectrum Lab (tnx Wolf !) was used to export FFT data, in a similar way of the Markus' OPDS setup.
Other programs,  written by Markus,  were used: one  to convert FFT exported data for the EbNaut entry and another to search for the best frequency and time offsets.

There was not much phase drift during the qso and in other test transmissions, since we reach a good frequency stability at both ends thanks to Rubidium Reference Oscillator (Markus side) and a good quality OCXO from my side.

You can see reported symbol / carrier EbN0 and also the messages exchanged,  in the attached screen-shots taken at both ends.

We hope now to joint other stations that want to challenge the timing and frequency accuracy, to have a QSO in LF close to the Shannon limit.

Markus DF6NM, will report soon all particulars and his comments of the experiment. Thanks in advance Markus!

73, Domenico (iz7slz)




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