[RFI] Investigating receive noise - got a few questions

[Jim Brown]

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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