Thanks Wolf, lots to read up on, excellent information on
learning
how to use SL for these slower speeds. Also thanks for
pointing me to Stefan's site regarding the configuration
files for QRSSS, I wondered if anyone still had them
available.
I recall playing with SL's ability to use VLF stations to
lock onto but
they were too weak here in Canada. I do have GPS on my Tx
now
but I still see some un-explainable instability over a
period of 4-5hrs
but far less than 0.05Hz...so maybe not an issue when I
was using
file 8270Hz_QRSSS_4mHz.usr. Not sure what equates to in
QRSSS
though. I find that if I try anything like
'VLF_Soundcard_32K_47uHz.USR'
it takes several hours to load up in SL but I guess that
stands to reason...I hope.
Regards
Jack Askew
From: "Wolfgang Büscher"
<[email protected]>
To: "rsgb lf group"
<[email protected]>
Sent: Saturday, January 6, 2018 10:42:14 AM
Subject: SL settings for QRSS (was: Re: LF: RE:
Todmorden receiver by Jack)
Hello Jack and all,
you wrote:
>It comes back to using something like SL with its QRSS
capabilities. I wish I had a good file that worked at 8720kHz
for QRSS600 as an example. This would be a good start if
nothing else.
<
It's not that difficult to set up. The key point in SL to get
into the
microhertz-resolution is the decimation (of the sampling
rate), along
with complex frequency to have a complex FFT spanning just a
few Hz
around the "frequency of interest". The effect is similar as a
super-long FFT (concerning the frequency bin width, and thus
the
"gain"). I think on Stefan (DK7FC's) site you can find some
configuration files for QRSSS.
Back in the "old days" of extremely slow Morse, I wrote this
short
how-to (for Spectrum Lab):
http://www.qsl.net/dl4yhf/speclab/qrss_quickstart.htm
(it shows how to pick one of the VLF transmitters to
stabilize the
soundcard's sampling rate,
a bit out of fashion since good GPSes with sync output
became
available, but anyway..)
To make the FFT window even longer / frequency bins even
shorter than
used in the default settings,
use the option 'complex input for the FFT with internal
frequency
shift', as shown at
http://www.qsl.net/dl4yhf/speclab/settings.htm#fft_size
And, last not least, there an explanation of FFT length,
decimation,
windowing functions, resulting resolution / effective receiver
bandwidth
versus dynamic range, etc:
http://www.qsl.net/dl4yhf/speclab/fftinfo.htm
All the best,
Wolf DL4YHF
