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Date: Sun, 06 Jun 2010 23:19:29 +0200
From: =?ISO-8859-1?Q?Wolfgang_B=FCscher?= <dl4yhf@freenet.de>
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Subject: Re: LF: Soundcard frequency calibration for 8.97kHz tests
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Hi Roger and group,

I will try to explain the procedure in simple words, as soon as time 
permits, possibly tomorrow.
A (probably too long) detailed explanation of how the continuous 
sampling rate 'calibration' in Spectrum Lab works is here:

http://www.qsl.net/dl4yhf/speclab/frqcalib.htm#continuous_sr_calib_principle

If you use Markus's configuration, you will not have too fiddle around 
with the fine tuning, since most (if not all) is already properly set up 
there.
How to select one of the VLF MSK transmitters as a reference:

Select 'Components' .. 'Sampling rate detector' in the main menu.
There's a field labelled 'Reference frequ.'. It contains a list of 
preconfigured ref signals. Selecting any of them also sets a few other 
parameters (like MSK bitrate, etc).
Set the checkmark 'Enabled', click 'Appl', and wait for the status panel 
(on the bottom of that window) to turn green. If it doesn't.... we'll 
get back to that later.
If all works as it should, switch to the 'Scope' window (still inside 
the "Calibration" window). If your VLF receiver really picks up one of 
the military transmitters, there must be two "peaks" in the special 
spectum display, about 10 dB above the "noise" (which is in fact the 
pseudo-random modulation).

Depending on how "far off" the soundcard is (and some of them are 
really, really far off the nominal sampling rate), you may need to 
increase the tolerance in ppm (labelled 'Max deviation from initial 
sample rate').

More later,
  Cheers, Wolf .



Roger Lapthorn schrieb:
> As a novice on calibrating sound cards to ensure a very stable 
> 8970.00kHz frequency, can some spell out, simply, the procedure to do 
> this? I'm pretty sure my RX loop/preamp set-up is now sensitive 
> enough, so I'd like to get set up to receive Stefan and others during 
> future tests.
>
> I'm sure others would also appreciate a simple step-by-step guide or 
> at least being pointed to somewhere where this is clearly and simply 
> described.
>
> Thanks in advance.
>
> 73s
> Roger G3XBM
>
> -- 
> http://g3xbm-qrp.blogspot.com/
> http://www.g3xbm.co.uk
> http://www.youtube.com/user/g3xbm
> G3XBM    GQRP 1678      ISWL G11088