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Date: Sat, 24 Mar 2018 18:01:07 +0100
From: DK7FC <selberdenken@posteo.de>
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To: rsgb_lf_group@blacksheep.org
References: <16254e122f1-c8b-18d3d@webjas-vad169.srv.aolmail.net> <5AB5F6A3.10109@posteo.de> <579355A36AEE9D4FA555C45D556003ABA3C3D00B@servigilant.vigilant.local> <ed810880-497b-e818-dc62-c8ab002e9a15@n1bug.com>
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Subject: Re: LF: K3RWR LF EbNaut in CT
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Hm, let me try.
I'm not an expert on all rigs and software components which can do the job.
I try to repeat some basically things.
There is the way to use Linux and Windows for EbNaut generation and 
reception. Linux clearly offers more functions and performance but 
Windows is simply more common on the currently active RX and TX sites. 
So let me focus on Windows.
VLF reception is easier regarding frequency stability because you just 
need to lock the soundcard to a source of absolute stability. The 
easiest method is to use a cheaply available GPS module. I'm using the 
old NEO-6M version here on almost any site (RX and TX) but i heared 
about modules of higher performance and functionality, such as the 
NEO-7M or 7N. Other may add their comments. For example IW4DXW ( i 
think) took a NEO-7N as a LO frequency generator, which will be 
necessary for LF reception, at least if you are one of those preferring 
to build their own RX/TX stuff.
I have no idea about HDSDR or commercial receivers.
SpecLab allows to export FFT data into small txt files which can be 
converted into wav files using tools by DF6NM. These wav files can be 
evaluated in the Windows version of Paul's EbNaut decoder. This is the 
way as many VLF/LF operators do it.
A txt file has a size of e.g. 369kB, so you can easily generate a file 
per hour, for several weeks, and try to decode an announced message later.
As long as the audio out of your LF converter is free from frequency 
offsets, drift and phase glitches, then SpecLab and your PC built-in 
soundcard can do the rest. So the investment is not dramatic.

If you don't trust the stability of your hardware, just make a test and 
run a carrier from an absolutely stable signal source and try to decode 
a '*' message in EbNaut.

The EbNaut decoder will need a wav file to search the message in. And 
for Windows i currently know only one method to generate these files 
(including the correct header in the correct format): SpecLab and 
Markus' tools. And SpecLab is a tool working together with soundcards or 
virtual audio cables of course. I use VAC and have no problem with SR 
glitches but i'm passing the ref signal through VAC as well, so SpecLab 
is the backend and will correct eventual glitches.

A lot of text already. I hope it was not do difficult and helped a bit...

73, Stefan

Am 24.03.2018 15:12, schrieb N1BUG:
> On 03/24/2018 09:18 AM, VIGILANT Luis Fernández wrote:
>
>    
>> Anyway would be interesting to discuss the hardware needed for
>> decoding EbNaut in LF Would help others to figure out how to
>> start using their stations already decoding WSPR, etc
>>      
> Yes, please! We need help!
>
> I have similar questions as Luis.
>
> I'm using a simple home built SDR feeding I/Q to a sound card, HDSDR
> output to a virtual cable (VB Cable).
>
> Do I need to worry about sample rate correction on VB Cable? If so
> is there any way to do it?
>
> Do I need to worry about sample rate on the sound card which is
> receiving I/Q from the SDR? If so, is there any way to do it? Both
> left and right channel are in use.
>
> What about time stamping? There are some delays I think in HDSDR. I
> don't know if there is any way to work around this.
>
> I would need a more stable LO for the SDR than its present crystal
> oscillator! I still don't know how to do this at reasonable cost. I
> suppose it will require a GPSDO which could output 450 kHz or
> something around there, but I have no practical idea how to do this.
> The more I read, the more confused I become.
>
> By the way I have a HP 3325B. Is this of any use for either the
> receiver LO or for transmitting EbNaut? It has the internal high
> stability option but I assume this is nowhere near good enough. It
> can accept external reference at 1 or 10 MHz but I do not know if
> this can make it good enough for anything. It also has a Phase mod
> input, but I know nothing about this.
>
> 73,
> Paul N1BUG
>
>