Wolf et al - thanks for this - Ive been playing during lunch time here in Anchorage using Teamviewer and listening to the derived audio out of Spec labs and tweaking the NB Trigger levels in the last Black box in Spec LaB - with my set up
Ive set it to 10dB and average rise time constant on 5 secs (per recom) - that seems to (audibly) blank the lightning noise (actually not a lot here in Alaska at midday today which is kind of worrying :-) _ lower than this it severely cuts off and blanks too much off - per Pauls/Wolf suggestion I do have a 3Khz bandpass set in the blackbox between L1 and L2 - Im guessing noise content, color, levels and duration is untypical and empirically we have to deal with our own burbles..but base lines are a great start
Here Im using the audio out (nominal 1KHz offset for XBA) of the SLMS and not using direct sound card on this one - noise level background during the day is -106dBm and that seems only to vary a bit during the day - early evening actually isnt too bad and only when Asia Pac "opens" does it really get bad.
I do have a signalling system (probably power line) very close in to 29.499 which I can audibly here as a carrier - it appears to be on for about an hour and then off for a few mins - you can actually see on my VLF wideband snapper - I should really see if I can blank it out and put a short hole in the passband
Heres hoping my neighbor stays out of his garage and leaves his noisy lights off tonight -
thanks for everyones help
Laurence KL7L XBA/5 XPQ
Hi Paul and all,
Thanks for the notes about the importance of the impulsive noise blanker.
Since there are still a few windows users on the group, here's how to
activate the noise blanker in spectrum lab,
assuming that one of the "very slow" morse modes has already been picked
from the 'Quick Settings' menu:
Select 'Components' / 'Circuit window',
click on the 'DSP blackbox' between circuit nodes L4 and L5,
select 'Noise blanker',
make sure to connect the spectrum analyser to 'L5' (not 'L4', which
would be "before" the noise blanker).
The NB defaults should be a good starting point, but as Paul pointed out
we may need more aggressive blanking.
This is controlled by the "Trigger Peak/ Average" settings (10 dB by
default, "the less, the more aggressive").
Details about the noiseblanker settings:
http://www.qsl.net/dl4yhf/speclab/circuits.htm#noiseblanker To remove signals which may irritate the NB (like strong MSK
transmitters or local QRM), the FFT-based filter can be switched into
the signal path between 'L3' and 'L4'.
For a quick start, begin with a simple bandpass, say 3 kHz bandwidth,
centered around 29.5 kHz.
Details about that filter:
http://www.qsl.net/dl4yhf/speclab/filters.htm#fft_filter As soon as my work on the WSQ program has finished, I will make a
configuration file which works "reasonably well" for this location, and
post it on a website. But I think the settings used below 9 kHz will
work reasonably well, but don't forget you need soundcard providing at
least 96 kSamples/second (select that sampling rate for input in the
audio settings).
Good luck everyone,
Wolf .
