[TowerTalk] Weird RFI at remote location

[Al Kozakiewicz]

I had two intermittent noise sources that the NB was marginally effective on. One was the dishwasher, the other a flat screen TV. Not plasma, but an older LCD fluorescent backlit model.

Al
AB2ZY

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of K9MA
Sent: Saturday, January 02, 2021 10:36 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Weird RFI at remote location

On 1/2/2021 8:32 PM, Ignacy Misztal wrote:
> 1. The noise is originating from one location because otherwise NB
> would not be able to blanket it.

I don't think so, unless you are using some sort of noise cancellation 
with two antennas etc. Noise blankers can be very effective against 
impulse noise, typical of line noise. However, they don't work well if 
there are strong signals within a few kHz. While it's a good diagnostic 
sometimes, a noise blanker that works on a quiet band probably won't be 
useful during a contest.

Besides its impulse nature, line noise is usually quite broadband. While 
it may affect one band more than another, there generally isn't much 
variation in strength within a band. This is very unlike noise from 
switching supplies, motor drives, etc, which usually show peaks at 
harmonics of the switching frequency, often 10-100 kHz. As others have 
suggested, the difference is most readily apparent with a spectrum 
display. It's a lot harder to discern by tuning around looking at the 
S-meter, though it can be done.

Because I live in the city surrounded by overhead power lines, I have 
way more experience with line noise than I'd like. Hopefully that will 
be of some use to others.

73,

Scott K9MA

-- 
Scott  K9MA

k9ma at sdellington.us

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