Question about RF noise

[RFI-EMI-GUY]

Good point about grow lights. That brings up a potential danger if you don't know your neighbors in a rural area and you stumble on their grow house.

We were house hunting locally and a house for sale nearby had some unusual modifications to all the rooms, including what appeared to be black out walls removed from the garage. I took a look in the breaker panel and found a breaker marked "grow lights" in magic marker.

The ARRL had an article in a past issue of QST about grow lights.

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[RFI-EMI-GUY]

A portable AM radio might be helpful. One with a large ferrite bar antenna. You can use it to null the signal and get an azimuth from several points and triangulate to the source.

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[Murphy625]

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.

I do have a smart meter.. but why would it start transmitting when the sun goes down and then stop when the sun comes back up?

I'm kind of stuck on that... The LED and CFL idea was a good one except I don't think even a horribly bad LED or CFL would transmit so far with such power..

Keep in mind, the properties around me are all 5 to 100 acres in size and I'm in the middle. This isn't suburbia or apartment-land here.. I think a deer farting would produce more interference than some screwy CFL bulb a 1/2 mile away...

When operating my ICOM 746 off battery power, I can see the noise when I turn on the basement lights.. There's about a dozen of them and they're all corkscrew CFL's.. They do create a bit of extra RF noise but didn't bother me or impede my ability to pull a signal in.

I think I'm going to re-orientate my dipole antenna and see what happens.. The middle is about 60 feet up in a maple tree while one end is about 20 feet off the ground and the other end is about 40.. Not only are the legs of the inverted V not even close to symmetrical, but the entire thing has a horizontal tilt to it. Gotta work with what trees I have right?

The wires are also running east and west.. I'm in Michigan and I've noticed I pull in a lot of signals from the southern states like Florida, but almost never anything far out west like California. Seems to be pulling signals in off the sides and not so much from the ends.

In fact, I bet if I plotted out the call signs I've heard, I'd find a cone of about 30 degrees going directly south.

 

[eorange]

Are there any flickering mercury or sodium vapor lights nearby? I had one by me, which helped the noise floor a little after it got fixed. That might explain the sundown/sunrise observation.

 

[Murphy625]

Are there any flickering mercury or sodium vapor lights nearby? I had one by me, which helped the noise floor a little after it got fixed. That might explain the sundown/sunrise observation.

No.. Nothing.

The only lights that can be seen is a small glow from town a few miles away if the conditions are right.

In the winter when the trees are bare, I can see lights coming from the window's of neighbors several hundreds of yards away.

After spending 4 nights on this, I'm leaning towards it being something related to my antenna and its interaction with the atmosphere..

 

[RFI-EMI-GUY]

No.. Nothing.

The only lights that can be seen is a small glow from town a few miles away if the conditions are right.

In the winter when the trees are bare, I can see lights coming from the window's of neighbors several hundreds of yards away.

After spending 4 nights on this, I'm leaning towards it being something related to my antenna and its interaction with the atmosphere..

If you are thinking precipitation static, a neon bulb will flash when attached to the coax. If you already have a gas discharge, or arc protector, it could be firing. Or the arc could be breaking down the insulation in the coax or connector. Then put a resistor, say 47K across the antenna to leak off the charge. Otherwise I cannot think of any other atmospheric interaction that would give you a 5 KHz spike across the entire range.

Don't discount the distance an LED lamp or other device can emit RFI. Take a portable AM radio and walk away from your home and toward the noise.

 

[Lauri-CoyoteFrostbite]

I highly second doing a 'walk about' with something to try and trace down the source- a portable radio is an easy first choice.
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Not that this is likely at all in your case Murphy, but quite a few of the high power'd radars I have work'd with would cause holy hell with any radios for surprisingly very long distances. And very broad banded --like your annoyance.
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Hmmmm-- happens at nite?... there aren't any strange lights that hover over your house after dark, are there ? Saucer shaped apparitions ? (Smiles) ------------ can't discount anything
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But seriously, check it out with a portable radio....

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Lauri

 

[RFI-EMI-GUY]

I highly second doing a 'walk about' with something to try and trace down the source- a portable radio is an easy first choice.
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Not that this is likely at all in your case Murphy, but quite a few of the high power'd radars I have work'd with would cause holy hell with any radios for too surprisingly long distances.
.
.
.
Hmmmm-- happens at nite?... there aren't any strange lights that hover over your house after dark, are there ? Saucer shaped apparitions ? (Smiles) ------------ can't discount anything
.
But seriously, check it out with a portable radio....

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Lauri

UFO's like to tap power off of transmission lines!

 

[AB4BF]

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.

"I do have a smart meter.. but why would it start transmitting when the sun goes down and then stop when the sun comes back up?

I'm kind of stuck on that... The LED and CFL idea was a good one except I don't think even a horribly bad LED or CFL would transmit so far with such power..

Keep in mind, the properties around me are all 5 to 100 acres in size and I'm in the middle. This isn't suburbia or apartment-land here.. I think a deer farting would produce more interference than some screwy CFL bulb a 1/2 mile away...

When operating my ICOM 746 off battery power, I can see the noise when I turn on the basement lights.. There's about a dozen of them and they're all corkscrew CFL's.. They do create a bit of extra RF noise but didn't bother me or impede my ability to pull a signal in.

I think I'm going to re-orientate my dipole antenna and see what happens.. The middle is about 60 feet up in a maple tree while one end is about 20 feet off the ground and the other end is about 40.. Not only are the legs of the inverted V not even close to symmetrical, but the entire thing has a horizontal tilt to it. Gotta work with what trees I have right?

The wires are also running east and west.. I'm in Michigan and I've noticed I pull in a lot of signals from the southern states like Florida, but almost never anything far out west like California. Seems to be pulling signals in off the sides and not so much from the ends.

In fact, I bet if I plotted out the call signs I've heard, I'd find a cone of about 30 degrees going directly south."

As you said, You run your power on solar cells during the day, and I'm assuming (I know, I know) you run your household power off the electrical grid at night when the solar cells don't work. That's when you start having the spike interference. That power coming off the grid goes through the smart meter at night. I'm no detective, now, but I played one 44 years ago. I would start there and make certain that nothing in the house is RF-ing (like you found the CFLs ) before I start looking outside at power pole insulators, loose crimp connections and things like that on your grid. Like I and several others who are way smarter than me have suggested, use a portable radio for the interference detection.
Good luck, my friend!

 

[RFI-EMI-GUY]

There is only one way to solve this , a battery operated portable receiver, turn off all your own stuff including the solar panels, open whatever breaker or link that disconnects the panels, the invertor. You want your stuff stone cold. Turn off UPS for computers and routers.

Still got noise? You have some walking to do.

No noise? Hmm, think about all the tech in your house and switch it on one by one.

There is no other way.

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[RFI-EMI-GUY]

When you find it come back and tell us. Don't be like the guy in Michigan who had everybody worked up about his 220 MHz repeater being desensed. He either fixed it, too ashamed to tell us what it was, or died trying.

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[Murphy625]

Well, I still haven't found it.... The AM radio thing didn't show anything. I'm thinking it might be power supply related or maybe something in the hardware maybe.

What I have done however is to realign my G5RV antenna so that the ends are pointed north and south and I'm now pulling in signals from the east and west.. I'm not seeing any great loss on the south side as I just heard Alabama.. But now I'm hearing Arizona and Colorado as well.. and someone speaking Spanish.. and that was just from 10 minutes of listening.

The 5khz spikes are still there but it does seem as though my western signals are far stronger.

 

[RFI-EMI-GUY]

Is your receiver an SDR dongle??

Well, I still haven't found it.... The AM radio thing didn't show anything. I'm thinking it might be power supply related or maybe something in the hardware maybe.

What I have done however is to realign my G5RV antenna so that the ends are pointed north and south and I'm now pulling in signals from the east and west.. I'm not seeing any great loss on the south side as I just heard Alabama.. But now I'm hearing Arizona and Colorado as well.. and someone speaking Spanish.. and that was just from 10 minutes of listening.

The 5khz spikes are still there but it does seem as though my western signals are far stronger.

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[Murphy625]

Is your receiver an SDR dongle??

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Yes.. Its an RTL-SDR hooked to a G5RV hanging about 50 to 60 feet up.

I should note that having a spectrum analyzer while I'm tuning frequencies and playing with filters has been great.. it will make me better with the ICOM 746 next time I fire it up.

 

[RFI-EMI-GUY]

Yes.. Its an RTL-SDR hooked to a G5RV hanging about 50 to 60 feet up.

I should note that having a spectrum analyzer while I'm tuning frequencies and playing with filters has been great.. it will make me better with the ICOM 746 next time I fire it up.

Is this the only receiver you have hooked up to the G5RV and seen these spikes? Things that come to mind:

Overload of the SDR dongle due to being contented to a multiband antenna without any preselector. Conducted common mode noise from the SDR power supply or the laptop PS that has a 5 KHz noise component.

Please hook up your 746 and see if you have same spikes.

 

[Murphy625]

Is this the only receiver you have hooked up to the G5RV and seen these spikes? Things that come to mind:

It is the only receiver hooked to it currently but I have had my ICOM 746 hooked to it and it works fine so far as I can tell... I bought this antenna FOR the ICOM.. Well.. truth be told, when tuning the ICOM in the 40 meter band, there are all kinds of funny noises as I traverse through the band so I wouldn't really know.

Overload of the SDR dongle due to being contented to a multiband antenna without any preselector.
Conducted common mode noise from the SDR power supply or the laptop PS that has a 5 KHz noise component.

Please hook up your 746 and see if you have same spikes.

But why would it not start until the evening when it gets dark? Wouldn't all those things be 24hr per day issues?
This is what's confusing me.. This ONLY starts in the evening after the sun has gone down. I'm beginning to think this is just standard noise and the SDR dongle is amplifying them and then displaying those spikes and I'm not used to seeing them.. But 5khz seems a bit too symmetrical to be random.

I tried using the laptop on battery power only and they still show up.. Wish I could take the laptop and drive around to see if anything changes but G5RV antenna's are a bit problematic to mount on a vehicle.

The other night, I let it sit on 40 meters and did not touch a single control.. I took various screen shots as the spikes grew.. around 30 minute intervals or so.

Next time I pull the ICOM out, I'll check it.. for now though, the battery I use for it is in a boat.

Check out the screen shots..
1st Picture 40 meters @ 5:57pm (pretty much every spike is a legit signal)
2nd Picture 40 meters @ 6:26pm (the weeds are starting to grow but not too bad yet)
3rd Picture 40 meters @ 6:42pm (the weeds are growing fast)
4th Picture I took tonight at 12:55AM (the spikes are as big as they'll get)

In the 4th picture, the modulated signals are still visible but are being overcome by noise.. only the strongest survive and the rest are buried.

Bye the way, thanks for your help, its much appreciated..

 

[RFI-EMI-GUY]

SDR receiver dongles are basically "naked" to the antenna. They have a propensity for being overloaded because ALL OF THE ENERGY present on the antenna is presented to the SDR front end. Better receivers have band switched filters between the antenna and the front end.

The new ICOM IC-R8600 for example is a superior SDR radio and its 14 bit A/D convertor is fed with 11 bandpass filters in the HF band and 13 bandpass filters in the VHF/UHF bands; From the product brochure:


Superb Receiver Performance
The IC-R8600 has 11 discrete RF bandpass filters in the HF bands
and 13 bandpass filters in the VHF/UHF bands. To prevent overflow,
only the intended signal is passed, while any out of range strong
interference signals are rejected. The IC-R8600 provides +30 dBm
IP3 and 105 dB dynamic range at 14.1 MHz. IP3 performance is +10
dBm at 144 MHz and 0 dBm at 440 MHz.



https://www.icomamerica.com/en/downloads/DownloadDocument.aspx?Document=865

With 11 filters, up to 30 MHz the ICOM only looks at about 2.7 MHz per band.

Your G5RV is likely picking up way too much signal which changes with time of day, and the A/D convertor inside the SDR Dongle is going nuts.

You will normally hear funny noises tuning 40 meters, but I think the 5 KHz spur might actually be your SDR internally generating these spurs as the aggregate 160-10 meter signals are increased. You can experiment with an external resistive attenuator to see if you can get those spurs to go away. Otherwise I would dust off the trusty ICOM and tune around.

You can buy external preselectors to use with your SDR. There might even be some 70's vintage accessory that will work well.

 

[RFI-EMI-GUY]

Here is a commercial solution for SDR.
You can make your own.

https://www.rtl-sdr.com/tag/preselector/

 

[RFI-EMI-GUY]

No shortage of products for SDR:

https://www.ebay.com/itm/151894217160?rmvSB=true

 

[Murphy625]

SDR receiver dongles are basically "naked" to the antenna. They have a propensity for being overloaded because ALL OF THE ENERGY present on the antenna is presented to the SDR front end. Better receivers have band switched filters between the antenna and the front end.

The new ICOM IC-R8600 for example is a superior SDR radio and its 14 bit A/D convertor is fed with 11 bandpass filters in the HF band and 13 bandpass filters in the VHF/UHF bands; From the product brochure:


Superb Receiver Performance
The IC-R8600 has 11 discrete RF bandpass filters in the HF bands
and 13 bandpass filters in the VHF/UHF bands. To prevent overflow,
only the intended signal is passed, while any out of range strong
interference signals are rejected. The IC-R8600 provides +30 dBm
IP3 and 105 dB dynamic range at 14.1 MHz. IP3 performance is +10
dBm at 144 MHz and 0 dBm at 440 MHz.



https://www.icomamerica.com/en/downloads/DownloadDocument.aspx?Document=865

With 11 filters, up to 30 MHz the ICOM only looks at about 2.7 MHz per band.

Your G5RV is likely picking up way too much signal which changes with time of day, and the A/D convertor inside the SDR Dongle is going nuts.

You will normally hear funny noises tuning 40 meters, but I think the 5 KHz spur might actually be your SDR internally generating these spurs as the aggregate 160-10 meter signals are increased. You can experiment with an external resistive attenuator to see if you can get those spurs to go away. Otherwise I would dust off the trusty ICOM and tune around.

You can buy external preselectors to use with your SDR. There might even be some 70's vintage accessory that will work well.

Ya.. I would have NEVER figured that out.. Not in my lifetime anyhow... Going to look into the filter thing and see what I can come up with.