[RFI] Mystery Noise (Aren't they all)

[Wes Stewart]

 Not letting a good thread die, here is some more info.
Here is a link to a Dropbox folder where, if it works, there are six files.  
https://www.dropbox.com/scl/fo/3c95ijqs0bs11i1mtveyc/h?rlkey=2wsbz4jkjo86a45n8fkjsy5lm&dl=0
Two of them are baseline plots taken from a Perseus SDR with the 160-meter antenna disconnected.  There is a spectrum plot and a waterfall plot.  Two others are the same setup with the antenna connected.  These are centered on 1840 kHz with a span of 320 kHz. There are two audio files recorded at two different frequencies using my Kenwood TS-890 in AM with a 10 kHz BW.  There is a fair amount of FFT averaging and smoothing on the spectrum plots but the waterfall shows the multiple frequencies in this mess.

Some, but not all, of the frequency shaping can probably be attributed to the antenna but this is definitely not what I would expect from powerline noise.  Has anyone seen anything like this?
Wes  N7WS

    On Monday, January 29, 2024 at 05:39:55 PM MST, Hare, Ed, W1RFI <w1rfi at arrl.org> wrote:  
 
 I agree; with no change, the noise is probably external, but do keep in mind that some UPS devices or devices connected to them may still be powered on, although in that case, I'd expect to see some change.

And no need for an apology.  Tracking down RFI can be darn tricky. If anything, you can be proud of having a mind open enough to backtrack and find what really is a minor misstep. When I worked in the ARRL Lab, many hams with RFI problems would not go back and look again at things they were "sure" they tested right.

You are going to find this.


From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of Wes Stewart via RFI <rfi at contesting.com>
Sent: Monday, January 29, 2024 4:55 PM
To: rfi at contesting.com <rfi at contesting.com>; dave at nk7z.net <dave at nk7z.net>
Subject: Re: [RFI] Mystery Noise (Aren't they all) Sadly, no.  A mea culpa and apologies to all who replied.  When I removed power to the shack, of course the KAT500 antenna tuner turned off.  I had put it in bypass mode, however, that wasn't good enough since it defaults to port one and my vertical was on port three.  So effectively, I disconnected the antenna when I removed power.  When I reran the test today with a jumper around the tuner, there is no change in the noise with the house un-powered.
I am satisfied that the noise is external.  

I don't know whether I can make attachments on this site.  If so, I have some screen shots.

    On Monday, January 29, 2024 at 09:10:35 AM MST, Dave (NK7Z) <dave at nk7z.net> wrote: 
 
 Hello,

This indicates that the RFI is in your home.  This is great news, it 
means you can fix it as fast as you want, and you don't have to wait on 
people...  Take a look at:

https://www.nk7z.net/i-have-rfi-now-what-locating-it/

I have a handy flow chart there that may help you locate the RFI...

Please report back on what you find it to be...

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 1/28/24 19:50, Wes Stewart via RFI wrote:
> In conversation with the tech a few days ago I offered to battery power
> my TS-890 and turn off the whole house breaker.  When I did the noise
> went from S9+10 dB down to about S4, but it was still there!


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