[RFI] Noise Level During Power Outage

[K9MA]

Hi Jim,

I've had some noise sources which were electronic, but most have been 
power line related. Besides the preponderance of 120 Hz harmonics in the 
AM audio, the very broadband nature of line noise is usually the main 
indicator.

73,
Scott K9MA

On 2/1/2023 2:33 AM, Jim Brown wrote:
> On 1/31/2023 9:21 PM, K9MA wrote:
>> My QTH is in an older residential area, surrounded by overhead power 
>> lines. Line noise is a constant problem. We recently had a major 
>> power outage, so I measured the noise levels to get a baseline with 
>> little line noise.
>
> Hi Scott,
>
> How do you know that it's line noise, not electronic noise? 25 years 
> ago, line noise was a good assumption for anything we heard on the 
> bands, but in almost any developed area, the average home has a couple 
> of dozen electronic sources, everything from switch-mode power 
> supplies for everything that plugs into the wall, variable speed 
> controllers for motors, computers and lots of other stuff with 
> microprocessors in them, and on, and on. When the power goes out, so 
> do all of those electronic noise sources (except for those that UPSs 
> keep running).
>
> The slides for talks I've done at Pacificon, Visalia, and to some 
> clubs, show how to use a well-adjusted waterfall to differentiate 
> between impulse noise (which is what line noise is) and electronic noise.
>
> http://k9yc.com/KillingReceiveNoise.pdf
>
> Yes, those with ear experience can nearly always tell the difference.
>
> NK7Z has wonderful advice and resources on his site about using 24 
> hour very wide waterfalls to yield clues about operating hours of both 
> impulse and electronic sources, and also recognizing multiple 
> electronic sources.
>
> 73, Jim K9YC
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-- 
Scott  K9MA

k9ma at sdellington.us