Message-ID: <56240DC7.80007@gmail.com>
Date: Sun, 18 Oct 2015 23:23:19 +0200
From: IZ7SLZ <iz7slz.domenico@gmail.com>
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To: rsgb_lf_group@blacksheep.org
References: <560DF24D.3050309@abelian.org> <0LmKOI-1aGjgI2N50-00ZuP1@mail.gmx.com> <CAA8k23T5Q+gnuPUZ=0ow-WKXomPbpzGYVNSx0Oqi1+iEXfLi=A@mail.gmail.com> <5623F0A0.9030902@abelian.org>
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Subject: Re: LF: Coherent BPSK on LF using EbNaut
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Status: O

Hi Paul, Markus  and all,

in this weekend i have made a simple modification at my LF TX to improve 
frequency stability.
I have phase-locked the 10 MHz OCXO of the exciter with the 10 kHz 
signal coming from the GPS.
Thanks to Markus DF6NM, signal was analyzed yesterday and today during 
some op-32 and Ebnaut transmissions. Modification seems working since 
Markus was able to decode me without changing frequency offsets.

I'm making now some EbNaut transmissions on 137502.24 Hz every hour 
(started at 10.00 UT). Message is composed by 25 characters at 1 s per 
symbol. Coding selected is 8K19A. Carrier starts 5 minutes before EbNaut 
sequence and ends at XX.30.
Power output is 100 W and antenna is inverted-L 8 meters high.
Signal should be visibile at DF6NM OPDS grabber 
https://dl.dropboxusercontent.com/u/26404526/opds.htm in the middle of 
the its right window.
I will stop the session tomorrow at 08.00 UT

So Paul, hoping that your receiver is completed and your antenna is 
already plugged in,  you can try to receive my signal. However let me know
if some  EbNaut-tx  parameters need to be changed and, of course, you 
can ask for a transmission at any time.

Thanks for your EbNaut great work.

73, Domenico / iz7slz


On 10/18/2015 9:18 PM, Paul Nicholson wrote:
>
> Spent some time today cobbling together a receiver for
> 137 kHz.   System noise measures about 4nV/m equivalent
> field strength in 1Hz with a BF245B front end but I've
> not yet attached it to an antenna - that's usually when
> the trouble starts.
>
> The mono audio input of the BT878 video card timestamps
> fairly well while sampling at 448k samples/second.  It's
> a bit noisy: 3.5 uV RMS in 1Hz at the line input, which
> means I needed to build in quite a bit of rx gain to
> overcome the card floor.
>
> Because it's a mono audio input I have to mix the GPS PPS
> and the LF, then separate them again in software.
>
> Hopefully soon then, some phase measurements at LF.
>
> -- 
> Paul Nicholson
> -- 
>
>