Doesn't look too good!
TOP TRACES: I believe the impulsive increase in baseline most obvious in
the top trace is due to normal sferics (lightning in the hemisphere). This
is quite normal.
BOTTOM TRACES: The 'loosy-goosy' moving tines are likely switchers from
somewhere within the near reach of your antenna. The nasty stuff in the
center is a real problem. Since the tines are stable, I doubt its a
switcher of any kind. Was this data taken with sun up and possibly any
close-by solar power installations 'working'? 17.6 kHz tine spacing is
certainly suspicious, but it is quite stable. Some sort of digital device
within reach of your antenna, but I couldn't begin to guess what it is.
GENERAL: Yes, you should sleuth the whole HF spectrum as some higher
emissions may be related to lower-frequency sources. I'd suggest a
batttery-powered portable radio with an external antenna. A good 'antenna'
for this sort of thing is a small (in relation to a wavelength) loop. They
have very sharp nulls in the plane of the loop good for DFing. The loop
needs to be large enough to be able to detect the interference but small as
a portion of a wavelength.
CONCLUSION: Sad to mention the obvious: You didn't excape the RFI the
digital 'revolution' has brought upon all HF frequencies. Please keep us
posted as to progress and results of any of your sleuthing. Pretty
clearly, it does not originate from you home, itself. The only other
thing I'd suggest is to run the same tests with your radio powered off a
battery and the entire house shut down, electrically, but you've pretty
much eliminated that. However,there could be something hiding in the
shadows.
A good portable 'receiver' could even be one of those cheap USB dongles
supported on a known quiet laptop and coupled to the loop I suggested.
That way, you could watch a good portion of the HF spectrum (2 MHz) at a
time. But, you will have to deal with laptop-generated noise. Even many
of the modern synthesized portable battery-operated radios produce their
own noise. Be careful where you hold the radio so you don't introduce
digital noise into the antenna from the radio. My portable receiver I use
for the purpose is very guilty of that.
Dave - WØLEV
On Sat, Nov 10, 2018 at 9:58 PM Andy KU7T <ku7t@ku7t.org> wrote:
> 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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> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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