New QRM appeared today on my server farm!

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KA1GJU
Posts: 258
Joined: Tue Aug 11, 2020 2:16 pm

New QRM appeared today on my server farm!

#1

Unread post by KA1GJU »

While fiddling with the RSP1A and it's needed AM BC filter, I noticed this mess on my screen. Was active this AM, then mid-day was off. Now this PM it's active again.
Peaks are at EVERY 6 kHz, which is a new one for me. The QRM drifts ever so slowly

I got the 1m diameter active loop and Yaesu FT-817 in action this afternoon, and narrowed it down to a few houses NE of me in a cul-de-sac . When the wind dies down, will do a drive by with the loop outside the truck, but rotatable by hand.

Here's a short movie of what I am up against.

73 Kriss KA1GJU
SDR Console 2023-05-17 17h 42m 45s.mp4
QRM at KA1GJU SDR farm
(4.33 MiB) Downloaded 94 times
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

Max
Posts: 830
Joined: Thu Aug 13, 2020 9:47 am

Re: New QRM appeared today on my server farm!

#2

Unread post by Max »

KA1GJU wrote: Wed May 17, 2023 9:53 pm While fiddling with the RSP1A and it's needed AM BC filter, I noticed this mess on my screen. Was active this AM, then mid-day was off. Now this PM it's active again.
Peaks are at EVERY 6 kHz, which is a new one for me. The QRM drifts ever so slowly
This has to be power supply/inverter of some sort. Fact it is off at midday........ do you have someone nearby who has solar panels and has perhaps added a solar storage battery? If it's there all (or most) of night but goes off during bright daylight hours I might expect a solar "hybrid" inverter or battery inverter. These battery storage systems will only become more common. In fact I'm thinking of installing one myself (home-built).

Also, I have a car (automotive) 12 volt car battery charger that I purchased on Amazon. The RFI from this thing is not at all unlike what you are seeing. It's appalling. The model type was actually mentioned in RSGB RadCom about a year ago from others seeing the same thing. Reported to Amazon (for what good it will do).

So much far-eastern junk electronics around with all of the RFI filter components omitted for a few pence cost saving! Also, my own washing machine (NOT cheap far-eastern junk..... German) also emits not dissimilar RFI when the drum turns, but not as strong as you are seeing. Again, my guess would be inverter driven motor.

Good luck finding it and, more importantly, shutting it up. Keep us posted. I for one am interested in the result.

Another thought........ electric vehicle charger?

Max

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KA1GJU
Posts: 258
Joined: Tue Aug 11, 2020 2:16 pm

Re: New QRM appeared today on my server farm!

#3

Unread post by KA1GJU »

Hello Max,
I got it narrowed down to a particular home with my active loop antenna. Luckily I know the neighbor to the south of the possible QRM'er, and texted him I was coming up the driveway to take bearings of my predicted source . The 1M loop was on a PVC pipe (mast) and anchored through the open window of my Ford F-150 inside door handle and the bottom rested inside the lower pocket in the door. So one hand on the wheel, the other on the mast looking for the sharp null with and Airspy HF Discovery and a laptop on the passenger seat.
The owner was not home (neighbor texted him) and they have a threatening German Shepard, so I didn't go up their driveway. There is a large motor home in the backyard (been there a long time), hoping he plugged in the AC cord and the charger/inverter/converter is the culprit. Those things are TERRIBLE at campgrounds when trying to work HF. Birdies EVERYWHERE! Or maybe a new EV? It was an S-9 on the 80M inverted vee of my IC-7610, broadside to the noise source!

Will take a pic of the truck with antenna, it's rather comical looking (nerdy?) tomorrow. :geek:

Here's my plots of nulls, the antennas of KA1GJU Super Station's.
Yellow lines are Super Station antenna fields w/the associated Super Station #.
The red lines are vectors of where the nulls were, the star was where the observation took place.

It shut down at some point this afternoon and hasn't returned. As far as I know, there are no solar panels anywhere (other than my own for repeater battery backup and diesel generator back up). Looks like some sort of charger or converter. The drifting frequency is very slow.

Will hopefully get on the property Friday or this weekend.

73 Kriss KA1GJU
Attachments
120m Band DF Null Plots
120m Band DF Null Plots
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

Max
Posts: 830
Joined: Thu Aug 13, 2020 9:47 am

Re: New QRM appeared today on my server farm!

#4

Unread post by Max »

KA1GJU wrote: Fri May 19, 2023 2:02 am It shut down at some point this afternoon and hasn't returned. As far as I know, there are no solar panels anywhere (other than my own for repeater battery backup and diesel generator back up). Looks like some sort of charger or converter. The drifting frequency is very slow.

73 Kriss KA1GJU
Hi Kriss

I had similar thing last weekend. I have pretty quiet RF environment but suddenly noticed unwanted RFI on 40m, and various other spots up and down. Slow drifting wide noise bars. Noticed nearish neighbours had just acquired hybrid EV so assumed the worst and that it would be ongoing from now on, but same as you just disappeared after about 24 hours and not come back since. Looked very much similar to my nasty cheap Amazon Chinese car charger so I'm hoping it was just my immediate neighbour charging a car battery, but it's always extremely annoying to suddenly hear an unknown noise source so I feel your pain!

Keep us posted as to the outcome. Some good DF skills there by the way. I'm actually dusting off an old Dell i5 laptop to use for exactly that purpose so I can shut off my own house power and maybe even track some self-made RFI, like my UPS for example. I know it's pretty much OK but I've had suspicion for a while that it may be throwing out something on AM (MF) bands. Not a biggie for me at the moment because that's not my "thing" but nice to keep a track on the background sources of QRM. I also will use it connected to an HF+.

73

Max

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