Message-ID: <002a01c1eae6$01d0e6d0$0700000a@parissn2>
From: "Stewart Nelson" <sn@scgroup.com>
To: rsgb_lf_group@blacksheep.org
References: <000101c1eaa3$7d1b6240$db72073e@default> <5.1.0.14.0.20020423145457.00aec130@gemini.herts.ac.uk>
Subject: Re: LF: Re: Re Jason .WAV files
Date: Tue, 23 Apr 2002 18:43:31 +0200
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Hi Jim and all,

The 1 kHz filter sounds like a good idea.  If you don't have
strong carriers dominating the audio, then 8 bit samples should
be fine.  Also, if you keep the audio frequency fairly low,
you can record at, or convert to, a lower sample rate.  If you
will be downsampling with software, please record the
original at 16 bit resolution, and convert to 8-bit samples
at the lower rate.

Fifteen minutes should be plenty.  At 5512 bytes/sec, that's
about 5 MB, and it will probably zip to about 4.  Even lower
sample rates should be fine if they don't lose data.

Alternatively, if you don't mind sending a CD-R to Paris,
then you need not worry about file sizes.

73,

Stewart KK7KA

----- Original Message ----- 
From: "James Moritz" <j.r.moritz@herts.ac.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, April 23, 2002 4:35 PM
Subject: Re: LF: Re: Re Jason .WAV files


> At 12:23 23/04/2002 +0200, you wrote:
> 
> 
> >Unless there is strong QRM on an adjacent frequency, please use
> >a wide (SSB) filter, and put the desired signal near the center
> >of the IF passband.  This makes it easier for impulse noise
> >rejection algorithms.
> >
> >Thanks,
> >
> >Stewart
> Dear Stewart, LF Group,
> 
> Using the usual "data" frequency around 137.5, the problem is the very 
> strong DCF39 signal on 138.83kHz. It is possible to receive in an SSB 
> bandwidth at my QTH, provided there are no local stations operating, but I 
> would have to have the filter bandwidth centered on about 136.5kHz. 
> Alternatively, I could use a 1kHz bandwidth filter. Another possibility 
> would be  to use the "transatlantic" slot around 135.9kHz, but in this 
> case, the problem would be the Datatrack beacons off the lower band edge.
> 
> Do you have a preference for a particular sample rate? How long a recording 
> do you need? I can E mail a few megabytes without too much trouble, but if 
> you need longer I will have to get the data burned onto a CD and mail it to 
> you.
> 
> Cheers, Jim Moritz
> 73 de M0BMU
> 
> 
>