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
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