[RFI] Screenshots of a wideband short pulse

[Scott Yost]

And adding to K1TTT's advice, when you turn off your own home's breakers give circuits that feed televisions at least a full minute before ruling them out as a culprit, as super capacitors in some of these devices will keep circuitry powered for many seconds and still emitting RFI.   Our Sanyo wall mounted TV taught me this lesson.   NM8R



________________________________
 From: K1TTT <K1TTT at ARRL.NET>
To: rfi at contesting.com 
Sent: Thursday, December 13, 2012 7:37 PM
Subject: Re: [RFI] Screenshots of a wideband short pulse
 
Probably something arcing.  Could be anything from a bad insulator on a
power line to a light switch, neon sign, street light, or a fish tank
heater.  First eliminate your house, turn off every breaker and watch for it
to stop... yes, this may take a while if the noise doesn't happen regularly.
If its not in your house then go mobile see how strong it is in the driveway
and then go a half mile or so in each direction and note strength, again,
this may take a while if it isn't being cooperative.  Hopefully at some
point you find it getting stronger and keep going that way until it gets
weaker then back up and start looking for the strongest source for possible
sources.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net


-----Original Message-----
From: Aaron Kreider [mailto:aaron at campusactivism.org] 
Sent: Thursday, December 13, 2012 22:39
To: rfi at contesting.com
Subject: [RFI] Screenshots of a wideband short pulse

I've got a wideband short burst noise.  It is very short - maybe 1/20th of a
second.  It affects everything from roughly 0 to 20 mhz.  It is weaker on
the higher frequencies and dies out around 20 mhz.  I'm getting it at random
intervals and a range of strengths. Sometimes there are 5 in a second and
sometimes it takes 2-3 minutes to see one.  
Typically it is 20-30 db over my noise level (3 mhz - 8 mhz - below that the
noise level is stronger).  It doesn't sound like lightning.  
Lightning lasts longer, whereas this is more of a blip noise.    Could 
it be an arcing loose wire?

I tested shaking the antenna to see if there is a loose connection. No luck.

I tested some traffic lights nearby as well.

Screenshots from my QS1R:

3.8 - 5.6 Mhz
You can see how much higher the peak noise level is (the grey line that is
20 db) over my regular noise level.  In the spectrum history, you can see a
blue and green horizontal line that crosses the entire band.  This is how it
regularly looks (by contrast the faint blue line on the bottom is not the
regular look).
http://www.campusactivism.org/images/pulse1.jpg

Another 3.8-5.6 mhz
http://www.campusactivism.org/images/pulse2.jpg
This shows three closely spaced pulses.

A weaker version of the pulse around 7-9 mhz.  I turned up the sensitivity
of the spectrum history so that it could be seen.  Again you can see how the
pulse's peak noise level is a lot higher than the regular noise (20 db+)
http://www.campusactivism.org/images/pulse-8mhz.jpg


2-4mhz
A weak version of the pulse at this range.  It can be stronger.
(You can also see vertical lines - I think I've got a touch lamp putting out
inteference, but it is very mild compared to this pulse).
http://www.campusactivism.org/images/pulse-3mhz-mild.jpg


Any ideas?  Are battery chargers this random?

Thanks,

Aaron
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