LF: Effects of noise burst

[Bill de Carle <ve2iq@magma.ca>]

I noticed my marker line was getting chopped up at times on both 
Spectrum Lab screens.  At first I thought it was another strong 
carrier off-screen for the SL display but still within the 500-Hz Cw 
filter's passband.  There are several clearly *audible* signals in 
there at times.  So I brought up ARGO for a wider view using 3-second 
dot mode.  You can see my marker at 136.170 Khz along with several 
other much stronger signals.  Around the middle of the time grab it 
seems as if everything went dead - in fact it was a 45-second burst 
of local noise.  Not much of anything audible but I saw the S-meter 
jump up about 30 dB (cutting back the RF gain and making the other 
weaker signals disappear).  Interesting how the background looks 
exactly the same during the noise burst as at other times.  We don't 
*see* any noise here, we see the *absence* of all the usual 
signals.  That noise is what chops up my marker lines on the two .usr 
spectrum lab screens.  Although still full daylight here it's getting 
near supper time and people are turning on appliances.  Things will 
quiet down later hopefully.  Here's the ARGO screen:
http://www.nrtco.net/~ve2iq/grabs/136argo.jpg

Bill, VE2IQ