[linrad] Linrad NB demo

[W3SZ <w3sz@xxxxxxxxxxx>]

Hello, All!

I tend to keep Linrad running when I am home (and even not home) to
monitor 144 MHz.  This morning the noise level was a bit higher than
usual, so I decided to take some gif and wav file recordings with Linrad
in SSB mode (to better show the noise), centered on the beacon at
144.283.

The top portion of the waterfall display will show the current signal
condition, and the main spectrum immediately below that will show the
current signal condition as well.  The main spectrum shows the signal
BEFORE noise blanking, and the waterfall and the high resolution
spectrum show the signal AFTER noise blanking has taken place.

Please note that my software is NOT optimally calibrated as I've had
trouble getting the pulser I built to work properly.  Nevertheless, you
can see and hear how the dumb and smart noiseblankers very effectively
get rid of noise here even in this suboptimal setting.  The performance
of the smart blanker is affected by the lack of optimal calibration.

Of course, going to weak signal cw mode and using the 20 Hz filter I
usually use totally eliminates this level of noise even without
blankers, but that is another strength of Linrad.

I usually have no idea of what  the noise level really is unless I look
at the main spectrum on Linrad, as the program so effectively
elliminates the noise I don't hear it or see it on the high resolution
display, where my eyes are usually focused.



The files are at:

http://www.qsl.net/w3sz/noblankers.gif
http://www.qsl.net/w3sz/noblankers.wav

http://www.qsl.net/w3sz/bothblankers.gif
http://www.qsl.net/w3sz/bothblankers.wav

http://www.qsl.net/w3sz/smartblanker.gif
http://www.qsl.net/w3sz/smartblanker.wav

http://www.qsl.net/w3sz/dumbblanker.gif
http://www.qsl.net/w3sz/dumbblanker.wav

Any questions or comments are welcome.

I will try again this afternoon to do a better job with the pulser for
calibrating, and if I get a better result will replace the files on the
website and repost a message after repeating the experiment when hi
noise conditions return.

PS Leif has a good demo the the NB during noisy EME conditions on his
Linrad website!

73,

Roger Rehr
W3SZ   FN20ah
2 Merrymount Road
Reading, PA  19609-1718
http://www.qsl.net/w3sz




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