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  #1 (permalink)  
Old 10-07-2018, 10:47 PM
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Default Question about RF noise

What would cause noise spikes at 5khz intervals (perfectly) across an entire spectrum from 160 meters all the way up into 2 meters ?? (and maybe beyond?)

It wasn't there earlier today but when I went to listen this evening, I had squealing noise spikes at 5 khz intervals from the very long wave lengths to the vhf band. (can't check any higher).

This is coming from a G5RV antenna though RG8/U.

I unplugged all the little transformers from the outlets and even tried turning off the CFL and LED lights.. nothing had any affect.
Thought maybe wife was running microwave or something but no.

The spikes are almost all the exact same size on spectrum analyzer display, perfectly spaced at 5 khz.. When getting to the 10 meter and 6 meter band, they start to change a bit where every other spike will be 1/2 the size.. but perfectly spaced at 5khz.

I didn't see this during the day... any ideas?
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Old 10-08-2018, 9:39 AM
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Might be a switching power supply like on a laptop or similar and it could be coming from a neighbors house. I would turn off all the breakers in my house one by one while monitoring to see if the noise stays or goes away, then proceed as necessary to find it.

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Originally Posted by Murphy625 View Post
What would cause noise spikes at 5khz intervals (perfectly) across an entire spectrum from 160 meters all the way up into 2 meters ?? (and maybe beyond?)

It wasn't there earlier today but when I went to listen this evening, I had squealing noise spikes at 5 khz intervals from the very long wave lengths to the vhf band. (can't check any higher).

This is coming from a G5RV antenna though RG8/U.

I unplugged all the little transformers from the outlets and even tried turning off the CFL and LED lights.. nothing had any affect.
Thought maybe wife was running microwave or something but no.

The spikes are almost all the exact same size on spectrum analyzer display, perfectly spaced at 5 khz.. When getting to the 10 meter and 6 meter band, they start to change a bit where every other spike will be 1/2 the size.. but perfectly spaced at 5khz.

I didn't see this during the day... any ideas?
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Old 10-08-2018, 10:46 AM
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A nearby plasma tv did this to a friend of mine.
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Old 10-08-2018, 11:06 AM
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My closest neighbor is 300 feet away, the next closest is about 1000 feet.

The 5khz signal is gone today.. I'm wondering if this is a natural event that happens only in the evening.. It totally saturated the HF bands and made them useless to me.
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Old 10-08-2018, 11:13 AM
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That sounds exactly like what happened to my friend with the plasma tv. It only happened from about 5:30pm-11:00pm. That's when the neighbor got home and turned his tv on. At bedtime he turned it off and the band cleared up.
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Old 10-08-2018, 12:04 PM
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Quote:
Originally Posted by Murphy625 View Post
My closest neighbor is 300 feet away, the next closest is about 1000 feet.

The 5khz signal is gone today.. I'm wondering if this is a natural event that happens only in the evening.. It totally saturated the HF bands and made them useless to me.
I doubt it is a natural event but I guess anything is possible.

For myself, I've encountered very similar that also extended darn near into the UHF bands.
It was evenly spaced like you are seeing and every spike was about as powerful as the other when looked at with a spectrum analyzer. The spikes only started getting shorter as I moved higher in frequency and my antenna was no longer resonant.

It turned out being from junk switching power supplies. In some cases it was from wall warts but in more than one instance, it was from switching power supplies located in consumer electronic devices such as flat panel HDTV's. Almost all electronic devices today use switching power supplies inside their housings.
Even some decent quality HF receivers like Icom's R75 come with switching type external power supplies these days. I was actually very surprised when I learned Icom was shipping them with the R75. If anybody knows how noisy they can be, I would think Icom's RF engineers would know.

Some switchers I've had in use were fine only to go noisy later in life. Like many devices, they have electrolytic caps in them that fail from heat or contain caps that are barely rated above the voltage they are running at. Then of course you have the older supplies that had bad caps in them from the time they were using caps with an unproven electrolyte material that would break down and fail early in life. Very common in computer motherboards from well known vendors as well as never heard of vendors!

Good luck finding the source. Switching off your mains or one breaker at a time for your home may be the best starting point as prcguy mentioned.
I've found many items in my own home ended up being responsible for bad noises I've experienced over the past several years. Turning off your power will usually reveal these noisy items but don't forget to account for battery powered items or UPS units that stay running while your breakers are off.

edit: I forgot to mention that what AD0TY said about Plasma TV's causing this is very possible. Plasma's were well known to cause bad RFI with similar spikes as you are seeing across several bands. Do they still sell Plasma TV's? I'd definitely check for this as the source though.
Even a neighbor at 300 feet could be the cause. His noise generator could be feeding back into the signal line like a cable tv signal cable and radiating back out from that several hundred feet away. Also items like outdoor lighting of all types can cause some pretty serious noise across several bands. I had a high pressure sodium street light that knocked out most everything when it came on each night. It radiated junk for several hundred feet away from the light and its power source came in underground! When I'd sniff the power lines where they came back above ground a 100 feet or so away, the noise level would shoot way back up indicating it was using the power lines as an antenna of sorts.
It turned out just being a bad lamp. They replaced the lamp only and the noise stopped immediately.

Last edited by kruser; 10-08-2018 at 12:13 PM..
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Old 10-08-2018, 2:28 PM
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If it happens again tonight, I'll be going on a hunting trip for the guilty party then.. and bringing a 2lb sledge hammer with me....
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Old 10-08-2018, 2:34 PM
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I would also check for new solar panel installations at your neighbors. The power inverters can make a lot of noise.
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Old 10-08-2018, 5:14 PM
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Quote:
Originally Posted by prcguy View Post
I would also check for new solar panel installations at your neighbors. The power inverters can make a lot of noise.
LOL. When it comes to solar installations, I'm the neighborhood know-it-all...

My entire home is run by an 8Kw grid-tied solar array. I installed it last year.. 14 feet wide, 40 feet long and makes more power than I use. The silly power company currently owes me over 2 Megawatts of energy from my surplus.

Besides, that would just affect things during the day when its making power.. Or if you're referring to the off-grid inverters, that would affect things at all hours of the day.

So far, I'm not seeing the same effect and its 6pm here... I'll know in another couple hours but I'm not seeing any hints of spikes showing up or growing.
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Old 10-08-2018, 6:03 PM
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Yup, the switching inverters would make the noise during the day. Anyway, shutting off the breakers in the house one by one will either find what room its in or prove its coming from the outside.

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Originally Posted by Murphy625 View Post
LOL. When it comes to solar installations, I'm the neighborhood know-it-all...

My entire home is run by an 8Kw grid-tied solar array. I installed it last year.. 14 feet wide, 40 feet long and makes more power than I use. The silly power company currently owes me over 2 Megawatts of energy from my surplus.

Besides, that would just affect things during the day when its making power.. Or if you're referring to the off-grid inverters, that would affect things at all hours of the day.

So far, I'm not seeing the same effect and its 6pm here... I'll know in another couple hours but I'm not seeing any hints of spikes showing up or growing.
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Old 10-08-2018, 6:18 PM
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The spikes back.. At about 6:30 pm, they started growing.... took about 20 minutes for them to reach full height..
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Old 10-08-2018, 9:47 PM
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Here's a screenshot.. Its like this all the way up to 144 and it doesn't start until evening until around 6:30pm.

I get better HF reception during the day than I do at night..
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Old 10-09-2018, 11:54 AM
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Not that it helps, but 40m at my house is totally quiet until that part of the day, and then picks up to S5 noise. Never looked at a spectrum scope, though....
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Old 10-09-2018, 1:20 PM
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Other thoughts to check for the source
Neighborhood Street Lamps?, Solar Walkway Lamps, Bug Zappers etc

If it takes Power, do not rule it out [battery or 120/240]
Quote:
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The spikes back.. At about 6:30 pm, they started growing.... took about 20 minutes for them to reach full height..
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Old 10-09-2018, 5:30 PM
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.
I'd try sniffing out the source.
.
Maybe use a 2 metre walkie talkie, or if you've a hundred, two hundred foot piece of something like RG58, attach your radio thru it to a small wire antenna- a small hand-held beam would be better- these spikes are showing up in the VHF range, No?..
.

Then play wildlife biologist; turn up the volume and go like you were tracking transmitter banded bats--- walk about pointing it at everything. Be sure to attenuate it down to minimal so you can hear the varying signal strengths- It will be like a "Fox Hunt.".
.
Good luck guy !
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Last edited by Lauri-Coyote; 10-09-2018 at 5:40 PM..
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Old 10-09-2018, 8:19 PM
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Quote:
Originally Posted by Murphy625 View Post
Here's a screenshot.. Its like this all the way up to 144 and it doesn't start until evening until around 6:30pm.

I get better HF reception during the day than I do at night..
Photocell switched LED lamps
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Old 10-10-2018, 1:51 AM
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Quote:
Originally Posted by RFI-EMI-GUY View Post
Photocell switched LED lamps
That sounds like a really good guess.. except I live in the country and there aren't any around here. No crime so no one keeps lights on at night around their house... at least not within 1500 feet of me.

How far could the RFI from an LED bulb travel anyhow? I mean, wouldn't it take something more than an LED light to create a 15db spike if it wasn't within throwing distance?
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Old 10-10-2018, 2:00 AM
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Quote:
Originally Posted by Lauri-Coyote View Post
.
I'd try sniffing out the source.
.
Maybe use a 2 metre walkie talkie, or if you've a hundred, two hundred foot piece of something like RG58, attach your radio thru it to a small wire antenna- a small hand-held beam would be better- these spikes are showing up in the VHF range, No?..
.

Then play wildlife biologist; turn up the volume and go like you were tracking transmitter banded bats--- walk about pointing it at everything. Be sure to attenuate it down to minimal so you can hear the varying signal strengths- It will be like a "Fox Hunt.".
.
Good luck guy !
.
.
Lauri
They're not nearly as bad on the higher frequencies.. Past 6 meters and they fade fairly quickly and aren't a problem.

I watched them very carefully this evening, and instead of hunting around the spectrum, I just kept my eye on the 40 meter band..
They don't just turn on.. its a slow process that takes an hour or so to happen. I've seen my grass grow faster.. but they do grow until they reach a maximum

I tried hooking up my laptop this evening.. no AC power, just battery.. and got the same exact thing.

Going to keep investigating tomorrow.
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Old 10-10-2018, 9:07 AM
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Do you have a "smart Meter" on your electrical entrance point? Use a small AM radio tuned to static between broadcast frequencies towards the high, 1.6 MHz end. Try it next to the meter and see if thats it. You may have to put a load on it like what you would normally run at night like lights, AC, stove, etc. to get it to radiate if you check it during the day.

A friend of mine with a spectrum analyzer found the frequency they use. Its 450 MHz here in our area. I can't remember the exact frequency - seems like it was 449.9 MHz.

They do go bad, lightning will play havoc with one but they are so expensive to the electric co. they do not like to change them out. I had one that was bad when they installed it. I had to get the manager to have it changed out. Once changed, no more problems.
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Old 10-10-2018, 9:48 AM
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Quote:
Originally Posted by Murphy625 View Post
That sounds like a really good guess.. except I live in the country and there aren't any around here. No crime so no one keeps lights on at night around their house... at least not within 1500 feet of me.

How far could the RFI from an LED bulb travel anyhow? I mean, wouldn't it take something more than an LED light to create a 15db spike if it wasn't within throwing distance?
How about grow lights, or incubators? Maybe an irrigation system? Geothermal system? (Like many others, a plasma tv/monitor is my first guess.)

How far it can travel depends on frequencies involved, and transmission mode. (Signals can travel quite a bit, via wire.) As broad of spectrum as you are seeing, it must have a nearby origin, unless it has an unusually strong source.

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