[Elecraft] P3 visualizing local noise

[Kurt Pawlikowski]

Jim, Fred, Et Al,

     Just a note: Some switching power supply "bricks" are noisy, even 
if the supplied unit is off. Had a View Sonic monitor like that. Because 
I could turn it off, It gave the false impression that it was not the 
source: The noise didn't disappear when "off," but some displayed images 
did modulate it differently. It wasn't until I disconnected the AC line 
that it went away. Unfortunately, that made me "internet" blind, so I 
usually just lived with it... {'-)

     Regards,

     kurtt

     Kurt Pawlikowski, AKA WB9FMC
     The Pinrod Corporation
     kurtt at pinrod.com
     (773) 284-9500
     http://pinrod.com

On 3/31/2011 01:30, Jim Brown wrote:
> On 3/30/2011 11:10 PM, Fred Atchley wrote:
>> My P3 started displaying persistent clumps of noise across each band. These
>> clumps reoccurred at about every 72KH over most bands.
> This is the signature of a switching power supply. They are everywhere,
> and most of them are noise RF noise generators. Spectrum displays like
> the P3 are very useful in exposing noise sources like these.  You find
> and eliminate one and you start seeing weaker ones. The noise comes and
> goes and you and your neighbors turn on and off the equipment powered by
> these nasty little buggers.  You'll also see them drift up or down in
> frequency as they warm up, and drift up and down as their oscillator
> frequency is dithered (frequency-modulated by noise).   RFI regulations
> limit the field strength at a single frequency. Dithering is a cheat
> that makes it easier to stay below those limits by spreading the noise
> over the dithered bandwidth.
>
> I recently identified the source of really loud noise on 12M as coming
> from the switching power supply for my SteppIR controller.
>
> 73, Jim K9YC
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