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
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