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Author Topic: RFI "signals" at regular intervals across all bands...  (Read 754 times)

KI6GEA

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RFI "signals" at regular intervals across all bands...
« on: December 09, 2021, 10:54:30 AM »

I have these pesky RFI signals equally across all bands (see photos)... I originally thought it was my switching power supplies, so I replaced them with a linear power supply, with no luck.

It had been suggested I shut power off at my house and run the radio off the battery, but I run a media company out of my home office (server) so this isn't a practical solution. I did power down my computer etc around my radio, and they are still there.

A friend also suggested it could be an AM station nearby, and I could try an AM band pass filter, but I see there are many and not sure what to buy...

Also I have a bunch of these ferrite choke sleeves, could I /should I just put them on the power cables on all the electronics in the house? Not sure of the best application of these.

Any other insight to a solution is very much appreciated. 73,

Chris
KI6GEA

https://photos.app.goo.gl/EiG9R9uFsaShp1acA

https://photos.app.goo.gl/9eXJMoe8TyJzA9ww7
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AE9DX

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Re: RFI "signals" at regular intervals across all bands...
« Reply #1 on: December 09, 2021, 11:12:15 AM »

I had a similar problem a couple of years ago. The first thing is to run the radio off a battery and see if the problem is still there. If not then it's probably coming in on the a.c. line. If it is, it could very well be a power line problem being picked up at the antenna. From the regularity of the pulse, it looks like it could be a.c. ripple. My problem turned out to be defective switch gear on a power pole about five poles down the road from my house. I called the power company and they were very cooperative about isolating the problem and repairing it at no cost to me. Just my 2 cents, Good luck!
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K0UA

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Re: RFI "signals" at regular intervals across all bands...
« Reply #2 on: December 09, 2021, 11:16:15 AM »

I can offer a little help, but not much. Need more information.

I can tell you it isn't the AM radio station. that is a blind alley.

BUT until you turn off every electronic thing, and I mean EVERY electronic thing in your home including any UPS battery backup devices, YOU WILL NEVER KNOW WHAT IS CAUSING THIS PROBLEM.   

Now as for the ferrites you have. Unless you know the mix that those ferrites are composed of, and I am betting your do not know the mix, then basically you don't have any ferrites. If you don't know the mix they are likely useless. You want mix 31 ferrites. BUT a hit or miss application or shotgun approach is not the way to go. It will be incredibly expensive and you will likely miss the real offender. AND you don't know if the offender is even in your home. Until you know that it is, and know which devices are causing this by turning them one one by one, your are just wasting time.

I heard and understand you don't want to turn off those servers. But could you schedule a downtime say 2:00 or 3:00 in the morning?  Make sure your problem is still there at that time, it could be solar panels and their inverters. Then run the rig off of the battery and go pull the mains to the house. Go around and shut down and unplug every UPS, Go back to the radio and see what you got. Hopefully it is clear. If it isn't, then the problem isn't in your house. And that is really really bad news.

Like I said, I am not much help, but hopefully I have given you something to think about
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73  James K0UA

KI6GEA

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Re: RFI "signals" at regular intervals across all bands...
« Reply #3 on: December 09, 2021, 11:51:05 AM »

This is actually very helpful, thank you so much for your time and experience.

I can offer a little help, but not much. Need more information.

I can tell you it isn't the AM radio station. that is a blind alley.

BUT until you turn off every electronic thing, and I mean EVERY electronic thing in your home including any UPS battery backup devices, YOU WILL NEVER KNOW WHAT IS CAUSING THIS PROBLEM.   

Now as for the ferrites you have. Unless you know the mix that those ferrites are composed of, and I am betting your do not know the mix, then basically you don't have any ferrites. If you don't know the mix they are likely useless. You want mix 31 ferrites. BUT a hit or miss application or shotgun approach is not the way to go. It will be incredibly expensive and you will likely miss the real offender. AND you don't know if the offender is even in your home. Until you know that it is, and know which devices are causing this by turning them one one by one, your are just wasting time.

I heard and understand you don't want to turn off those servers. But could you schedule a downtime say 2:00 or 3:00 in the morning?  Make sure your problem is still there at that time, it could be solar panels and their inverters. Then run the rig off of the battery and go pull the mains to the house. Go around and shut down and unplug every UPS, Go back to the radio and see what you got. Hopefully it is clear. If it isn't, then the problem isn't in your house. And that is really really bad news.

Like I said, I am not much help, but hopefully I have given you something to think about
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KI6GEA

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Re: RFI "signals" at regular intervals across all bands...
« Reply #4 on: December 09, 2021, 11:52:34 AM »

This is very helpful, thank you.

I had a similar problem a couple of years ago. The first thing is to run the radio off a battery and see if the problem is still there. If not then it's probably coming in on the a.c. line. If it is, it could very well be a power line problem being picked up at the antenna. From the regularity of the pulse, it looks like it could be a.c. ripple. My problem turned out to be defective switch gear on a power pole about five poles down the road from my house. I called the power company and they were very cooperative about isolating the problem and repairing it at no cost to me. Just my 2 cents, Good luck!
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W6QW

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Re: RFI "signals" at regular intervals across all bands...
« Reply #5 on: December 09, 2021, 03:01:24 PM »

Looks like a SMPS emission.  You'll want to get a time-domain assessment of one of the emission points to confirm. 
Take a look at my posting on July 18th:

W6QW link=topic=133486.msg1227863#msg1227863 date=1621309171

Good hunting...

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N7EKU

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Re: RFI "signals" at regular intervals across all bands...
« Reply #6 on: December 09, 2021, 03:34:19 PM »

Hi,

An old "transistor" AM radio can be a help in these situations.  Just tune it off-station and then bring it around to every wall wart power supply in your house.  All will make a little noise, but bad ones will show an increasing noise as you bring it closer -- and will really make a racket when you have it near!

This can help you narrow down the possible sources so you can target those with ferrites.

73

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Mark -- N7EKU/VE3

KH6AQ

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Re: RFI "signals" at regular intervals across all bands...
« Reply #7 on: December 10, 2021, 07:35:12 AM »

What you see is not an AM radio station. It is probably a switching power supply switching at 100 kHz.

Assuming it is coming from your house a way to locate it is to switch power off one circuit breaker at a time. As you cannot shut off the server power you won't be able to shut that breaker off. If this exercise does not shut off the noise source it is either on the server circuit or is outside your home. If you find a breaker that stops the noise, switch it back on and start unplugging things on that circuit to find the noise source.
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WB6BYU

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Re: RFI "signals" at regular intervals across all bands...
« Reply #8 on: December 10, 2021, 02:29:40 PM »

Quote from: KH6AQ

... It is probably a switching power supply switching at 100 kHz.




In that case, you can use a portable AM broadcast receiver tuned
to a multiple of 100 kHz, preferably where there isn't a local station.
You should be able to hear something as you tune through the band
if the interference is strong enough.  Then use that as a sniffer and
walk through each room, by any electrical cords, and see if you
find a spot where the interference is strongest.  You may have to
tune off frequency when it gets strong if the receiver gets swamped.

Of course, you can do this with any other receiver that covers the
affected frequency range.  The AGC in the receiver may make it
harder to detect the peak, but you should still be able to tell
"weak" from "strong".

I find a hand-held 80m DF receiver is convenient for this, even
though the loop antenna doesn't give accurate results in the house.
But not everyone happens to have one of those handy.


A friend of mine ordered a noise sniffer kit from Europe that does
this function in a couple of ways - it provides both AM detection of
the interference, so you can hear what it sounds like, as well as
an audio signal strength function that works on unmodulated
signals.  Unfortunately, I don't have the name of the unit handy,
but it is around here somewhere...

It was quite interesting to see which wall warts made the most
noise.  I have to unplug the power supply cord from one of my
desk lamps when I'm operating 2m.

KB1GMX

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Re: RFI "signals" at regular intervals across all bands...
« Reply #9 on: April 12, 2022, 12:17:20 PM »

Just looking at the pictures.

Its a switching power supply, How can I be so sure.  Its a periodic
signal that repeats at the switch rate of the device powered by that
switching supply.   

If it were a broadcast source it would be far greater spaced in
frequency.  What is in the pictures is not broadcast interference.

 it may be anywhere in the house even the heating/cooling system,
Others include the Laptop supply, cell phone charger, LED lighting
in the home, LED landscape lighting (more likely at night),
Lights with dimmers, Florescent laps with switching ballest, power
for the flat screen TV or even monitors on the server, battery chargers
for cordless tools (Drills, leaf blower, saws, vacuums...).

The first last and only is full house shut down. it needs to be only
for minutes.  Failure to do this leads to a drawn out process with
no answers.

Why?  There is the chance its not even in your house at all.  It
could be your neighbors!


Last item  Add a 1:1 unun/Choke balun to the antenna at the exist
of the house.  This is to reduce common mode noise that is on the
shield of the coax as it exists the house and is coupled to the antenna.

Allison
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W4NBO

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Re: RFI "signals" at regular intervals across all bands...
« Reply #10 on: April 13, 2022, 07:50:28 AM »

I am in the switching supply camp or some device similar. K0UA is correct, you have to isolate it. I disagree with calling the power co until you are reasonably certain its their lines causing the issue. Not very good PR otherwise. This does not look like 120hz (power lines) at all to me. You should be able to see the 120hz pulses on your SDR or I usually record the RFI and expand it out in audacity to count the 120hz pulses.

You could try to DF it with a small HF receiver. A small loop antenna which is easy to build helps a lot with a HF receiver DFing on the sharp nulls. Or even AM radio if the AM radio is picking up the same RFI. Using the AM radios figure 8 pattern loopstick to DF with the sharp nulls. You have to be very careful to DF the noise that is present in your HF station[/b]. Very easy to DF the wrong noise. Lots of trashy devices out there nowadays with near field emissions.

For me, firstly, I would shut off EVERYTHING including battery operated devices in my house first before anything else. Only takes a few minutes.
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WA2ISE

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Re: RFI "signals" at regular intervals across all bands...
« Reply #11 on: April 16, 2022, 02:02:56 PM »

Looks like ethernet RFI leakage. 
roughly every 60.8KHz.  Using shielded ethernet cable may help. 
NK7Z took a spectrum of such on 20 meters, which I show here.
See his page https://www.nk7z.net/rfi-snapshots/computing-devices/
« Last Edit: April 16, 2022, 02:09:35 PM by WA2ISE »
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