[RFI] Investigating receive noise - got a few questions

Hare, Ed W1RFI w1rfi at arrl.org
Mon Nov 12 17:29:01 EST 2018 

As ideal as it may sound to destroy every switcher, this is just not going to be a practical solution. Every electronic device in your home, from your LED bulbs to your TV and every modern appliance has switching supplies nowadays and only a small percentage of them are external. 

The only practical solution I can envision is to identify those that are causing you problems and if you can't replace them with analog supplies, assuming you can even find a suitable one, you will need to filter the wires with a combination of differential-mode and common-mode filtering.,

The emissions limits under Part 15 have not changed a whole lot over the years, so this is not a new rules problem, but a problem caused by the proliferation of devices that meet the rules and the more broadband nature of the emitters.

Ed, W1RFI



-----Original Message-----
From: RFI <rfi-bounces at contesting.com> On Behalf Of David Eckhardt
Sent: Sunday, November 11, 2018 3:40 PM
To: jim at audiosystemsgroup.com
Cc: Rfi List <rfi at contesting.com>
Subject: Re: [RFI] Investigating receive noise - got a few questions

If you're a ham and care about HF, just say no to any and all SMPS's!!!! !
!   They are everywhere.  And Part 15 was supposed to prevent this
happening.  Yea, sure,........ that's when FCC still cared!  Read my rant on my QRZ page.  35 to 40 years as an EMC / RFI Engineer sez it all.

Dave - WØLEV

On Sun, Nov 11, 2018 at 8:36 PM Jim Brown <jim at audiosystemsgroup.com> wrote:

> Good advice all around.
>
> More specifics.  1) Study my tutorial app note on this.
> http://k9yc.com/KillingReceiveNoise.pdf  2) Study the material on 
> NK7Z's website.  3) Your spectrum view is FAR too wide to tell much 
> about what you're seeing. I suggest that you start with 100kHz - 300 
> kHz views of the ham bands you care about the most. Then repeat all of 
> your turning off breakers tests. Do this with the assistance of 
> another ham -- one of you flips breakers, the other watches the 
> display and changes bands. 4) Search out and destroy (replace) every 
> switch-mode power supply in your own home. The average home has several dozen. 5) Repeat steps 1 and 2.
>
> 73, Jim K9YC
>
> On 11/10/2018 3:02 PM, David Robbins wrote:
> > The only thing I can tell from the first few seconds of that 
> > recording
> are
> > that the big wide pulses are probably lightning, though there is a 
> > possibility of local power line arcing.  It also looks like you are
> hearing
> > lots of actual band activity, sw broadcast and ham and other stuff, 
> > hard
> to
> > tell as the scales aren't readable to even know what bands you are
> listening
> > to.
> >
> > Some general things:
> >
> > 1. You can't clean up the whole hf spectrum so concentrate on the 
> > ham
> bands.
> >
> > 2. You can't see local noise when the bands are open, so check the 
> > high bands at night and the low bands at midday and when there 
> > aren't any thunderstorms in range.
> > 3. Most of the stuff you'll chase in your house will either be 
> > periodic spurs (harmonics of switching supplies or digital devices) 
> > or wide raspy crap from bad power stuff (if the source is in your 
> > house these can be dangerous, unless it's a furnace igniter maybe), 
> > note that cheap high
> power
> > stuff like battery chargers can make noise that wanders quite a bit 
> > 4. don't forget to unplug and turn off ups's, their chargers can 
> > make
> noise
> > if powered on, and their inverters can make noise if unplugged or if 
> > the breaker is off.
> > 5. Once you have cleaned up your own house then figure out if there 
> > are external noises that are interfering with what you want to 
> > hear... if
> there
> > are then you have the harder job of figuring out if they are nearby 
> > or dx 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:7373
> >
> >
> >
> > -----Original Message-----
> > From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Andy KU7T
> > Sent: Saturday, November 10, 2018 21:58
> > To: rfi at contesting.com
> > Subject: [RFI] Investigating receive noise - got a few questions
> >
> > Hi,
> > I am trying to sort out receive noise issues with my Flex.
> >
> > I am not exactly sure how clean the spectrum could/should be. I have 
> > the feeling that I may be more concerned about this just because I 
> > can see
> the
> > spectrum.  I am in an residenial area with 5 acre lots, with miles 
> > to the next town and businesses. I always throught/hoped I have no noise issues.
> >
> > I took some time last night to turn off all breakers, one after 
> > another, until only the shack was left. Then I reduced everything in 
> > the shack so
> the
> > only thing left was the 12V power supply, radio, computer and 
> > monitor.  I also adjusted the noise offset on the Alinco Powersupply 
> > with no changes, turned off the computer, and unplugged it. At this 
> > point any wall warts, modems, routers, etc were also  off. Still no significant changes.
> >
> > Take a look here at my spectrum, recorded while I turned off a 
> > breaker
> every
> > 30 s. There is no difference between beginning and the end:
> > https://1drv.ms/v/s!AiAwh4TnZjYMhtoFCHwTeJdHO2MFGw
> >
> > I really have not found any major decreases in hash or noise.  Here 
> > are
> my
> > questions:
> >
> >    1.  Do I go right about this at all?  Should I only look at the 
> > ham
> bands
> > instead of looking at the half the HF spectrum?
> >    2.  There is quite some pulsing/jumping of noise going on below 
> > 10 Mhz (see in video's top spectrum). Are those normal static 
> > atmospheric
> crashes
> > or something else outside I should be investigating further and if 
> > so
> how?
> >    3.  There are patterns around 4 - 5 Mhz that are definitely some
> patterns
> > from some device. Is it worth worrying about these, considering 
> > there are not near any ham bands of interest? Goes back to question 
> > 1 also: do I
> care
> > whats outside of ham bands?
> >    4.  I have some harmonics, some spikes between 12 and 15 Mhz. the
> distance
> > between the spikes is about 17.6khz. Any ideas what that could be? 
> > Is
> likely
> > not in my house though.
> >
> > Any tips and ideas how to proceed?
> >
> > 73
> > Andy
> > KU7T
> >
> > Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows
> > 10
> >
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-- 

*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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