Tag Archives: Radio Frequency Interference

Steve tracks down the source of persistent radio interference and gets it addressed

Photo via Unsplash

Many thanks to SWLing Post contributor, Steve Allen (KZ4TN), who shares the following guest post:


Tracking Down Radio Frequency Interference

by Steve Allen, KZ4TN

I first noticed the RFI in late November 2019 as a steady buzz at around S9. It was present over most of the high frequency spectrum. I waited until the second week of December to see if you would end on its own, no such luck. I put an HF rig in my truck and started driving around the area to see if I could find a potential source. About a quarter mile from my home is a 161 KVA substation operated jointly by the Tennessee Valley Authority and my local electrical utility. When I parked in the driveway outside of the gated substation the sound of the interference was very strong and blanked the HF spectrum. I called the phone number on the gate and after an explanation of why I was calling I was connected to a fellow radio operator. I explained the situation and he said he would bring the issue to someone’s attention and get back to me.

A week went by and I didn’t hear back from the TVA. I called the person I spoke with previously and he said that the individuals that he spoke with questioned the validity of my findings. He was very helpful but said he didn’t have much clout with the TVA, RFI investigations were not his area of responsibility. I told him I would be happy to meet with someone from the TVA and show them what I had found. I also said I would contact my local electric utility and see if they had an RFI detector so we could eliminate their equipment. My initial contact at the TVA said he would keep trying to get someone to take this issue on and work with me to investigate. I said I would call him back next week.

I then called the local utility company and talked to someone there who was familiar with these kinds of issues. The local utility company owns the output side of the equipment at the substation. He told me he was going to perform an infrared (heat) inspection of their equipment at the substation mid January as part of their annual maintenance and will also check the low voltage utility lines near the substation. I told him that I didn’t notice this RFI until after they had a power outage nearby. He said he would try and get over earlier and check the power lines that run along the streets and look into the power outage history for this area.

All during this time I kept a daily log of the RFI including time of day, frequency effected and S unit level. I also logged the weather conditions. To eliminate the electronics in my house as a possible source I connected my transceiver to a 12 VDC battery and shut off the mains circuit breaker, the RFI did not change at all. I also visited the ARRL webpage that provide information on RFI including recordings of known RFI:

http://www.arrl.org/radio-frequency-interference-rfi

The ARRL is the best source I have found in finding and fixing RFI.

By December 27th,  no word back from anyone. I assumed that they were off for Christmas but decided to write a letter to the TVA as a follow up to what had happened so far. In early January I received and email from one of the TVA engineers who said he would contact a field engineer who would contact me. The next day I received an email from the field engineer who said he was going to be in the area on another job but would meet me at the substation.

So, of course as soon as I am making headway with finding the problem the RFI diminished to the point of not being a problem. By this time here in Northeast Tennessee the winter temps are in the 40s and the humidity is lower. For whatever reason, the RFI ended. I met with the field engineer and we agreed that if there is no RFI there is nothing to search for.

Fast forward to August, 2020. In June and July I had been operating digital, mostly FT8. I usually had the volume control at zero and as it was summer I was doing no shortwave listening. One day I decided to tune around the bands and found that the RFI was back as strong as it was during December at S4-S9 from 2-30 MHz. I emailed the principal engineer I had previously been in contact with at the TVA and he told me he would contact another field engineer and that he would come to my house with an RFI locator and start a thorough investigation. The next day I received an email from the field engineer and we scheduled a time for him come over.

Upon his arrival he connected his RFI locator to my vertical antenna and tuned across the spectrum. The locator immediately displayed the signal. He captured an electronic image and said that he could now drive around the area and try and find a match. A hour and a half later he called and said he was unsuccessful and wanted to come back  and make sure the signal was still present. Sure enough, it still displayed on his locator and he was puzzled why he could not find a similar signal while driving the area. He said he would send a copy of the recording to the TVA engineer and get back to me.

A few days later I heard back from him and he wanted to come over again and make another recording. I believe after discussing this issue with his supervisor he was going to use a different method of searching the area. After a couple of hours I received a phone call from the field engineer telling me that he thought he had found the source of interference. Using a parabolic antenna he had found two different utility poles that appeared to have defective lightening arrestors on them. Both are within a quarter mile of my QTH. These poles are the responsibility of the local electrical utility not the TVA. He said he would contact them and follow up with me in a few days.

In a couple of days the interference was very low to nonexistent. Shortly thereafter the engineer contacted me saying the local utility company had completed the repairs and wanted to know if the interference was still present. I said I hadn’t hear it in a couple of days and I would get back to him if it returned. A couple of weeks later I received an email from the field engineer detailing the incident, what he had done to locate the interference, and what was done to repair it. In his email he stated the service was provided at no cost by the TVA Right of Way and Elizabethton Electric Department through TVA’s Comprehensive Services Program (CSP). I am so appreciative of the Tennessee Valley Authority. The airwaves are now free of manmade interference and I am looking forward to another winter of operating and listening to shortwave radio. Here in the 21st century there are so many electronic devices that are capable of causing RFI. I am very thankful that my station is RFI free (for the time being).

Steve Allen, KZ4TN
Elizabethton, TN


Thank you so much for sharing your story, Steve. Only recently, we posted Emilio’s article about tracing interference to poorly made switching power supplies. Thank you for sharing how you approached your local utility company, in your case, to resolve your RFI!

Very encouraging! Readers note that you don’t always have to live with persistent RFI. If you know the source isn’t coming from within your home, sometimes it’s simply a matter of getting your local utilities company to investigate.

Spread the radio love

Faulty TV to blame for 18 month broadband outage

Many thanks to SWLing Post contributor, Jeremy, who–in light of our recent discussions about RFI–shares the following news item from the BBC:

The mystery of why an entire village lost its broadband every morning at 7am was solved when engineers discovered an old television was to blame.

An unnamed householder in Aberhosan, Powys, was unaware the old set would emit a signal which would interfere with the entire village’s broadband.

After 18 months engineers began an investigation after a cable replacement programme failed to fix the issue.

The embarrassed householder promised not to use the television again.

The village now has a stable broadband signal.

Openreach engineers were baffled by the continuous problem and it wasn’t until they used a monitoring device that they found the fault.

[…]”Our device picked up a large burst of electrical interference in the village.

“It turned out that at 7am every morning the occupant would switch on their old TV which would, in turn, knock out broadband for the entire village.”

The TV was found to be emitting a single high-level impulse noise (SHINE), which causes electrical interference in other devices.

Mr Jones said the problem has not returned since the fault was identified.[…]

Click here to read the full story at the BBC.

Thank you for sharing this, Jeremy. I can guarantee that if the TV was emitting enough noise to interfere with broadband, it likely also affected the HF, MW, and LW radio bands!

What baffles me is the amount of time it took for the engineers to track down the source in such a small community. A skilled RFI engineer would have likely discovered what was causing the noise by looking at the spectrum analyzer–quite often the signal shape and frequency are indicators. In addition, a little signal “fox hunting” could have proven useful. With that said, noises aren’t always easy to locate and can travel along unexpected paths.

I certainly don’t blame the resident for remaining anonymous!

Spread the radio love

Post-storm power outage leads Emilio to find the RFI-spewing source of his problems

Storm with lighteningMany thanks to SWling Post contributor, Emilio Ruiz, who shares the following guest post:


Apprehending an RFI-generating monster!

At the beginning of the year, I was sad because, at home, an awful RFI noise appeared. The next few months the noise increase until S9!!. Day and night my receivers and my feelings were so dampened with this terrific RFI–only the lower Broadcast Band (900 to 540 Khz) was relatively immune to it.

Yesterday, we had a storm and the mains electricity service went off, so I connect a 12 volt battery to my RT-749b military surplus transceiver and the received signals were very clean like the “good old days”.

(Above: Listen W1AW loong distant from my QTH in Chiapas Mexico).

When the power electricity come back on, so did the RFI too!!

(Above: W1AW gone)

Remembering the recently publish post in SWLing Post about RFI, I did some testing by
cutting the electricity to my home (the main switch) and the RFI was gone!! So I discovered the RFI lives in my house–not in the outside wires!!

I put batteries in my old shortwave portable radio and searched (like Ghostbusters) all outlets contacts, one by one, connect and disconnected each device.

And I found the guilty party!

Exhibit A: The Mitzu laptop power supply

On December 2019, the power supply of my son’s laptop broke, so I bought a cheap substitute.

The RFI produced by this little monster could be heard at a distance of about 200 meters from my QTH!!! (Much like an old transmitter spark gap–!)

Even this cheap power supply apparently featured ferrite toroids on the wire but turns out it is fake!! It was only a plastic ball!

Exhibit B: Fake toroids!

The wires were also not shielded. No doubt one of the worst switched-mode power supplies I could have purchased.

Exhibit C: The Mitzu RFI generator wire without shield, only pair wires!

I found a old Acer power supply with same specs and I replaced out the RFI monster one.

And now? The shortwave bands are clean again.

(Video: Testing my Kenwood R-600 rx with Radio Exterior de España… plugging and unplug the Mitzu monster RFI generator).

So I wanted to share what happened to me, so perhaps it can be useful for other SWLing Post blog friends.

Watch these little switched mode power supplies from all devices in your home. Replace them if you detect RFI levels that harms SWLing. Consider disconnect all devices (vampire consumption–or phantom loads) if not in use; the radio waves and electric bill will be grateful to you!


WOW! What a difference! Emilio, that was great investigative work on your part. It’s as if that switching power supply was specifically designed to create RFI! No shield and fake toroids? That’s just criminal in my world! 

Thank you so much for sharing your story. Hopefully, this might encourage others to investigate and apprehend their own local RFI monsters!

(And by the way, Emilio, I love that RT-749b military transceiver!)

Spread the radio love

QRM-busting: Rob’s practical approach to tackling unwanted radio noise

Our good friend Rob Wagner (VK3BVW) over at the  Mount Evelyn DX Report has posted an excellent article on how to deal with man-made radio interference (QRM/RFI) in our homes and neighborhoods. This has been a frequent topic here on the SWLing Post (indeed, as recently as Thursday).

I’ve copied an excerpt from his article below, but I highly recommend reading his entire post which includes practical ways you can investigate and mitigate RFI within your home and neighborhood:

Mount Evelyn is a semi-urban, semi-rural location, about 45 kilometres east of Melbourne, the southeastern part of Australia. When we retired eight years ago to this lovely mountain region known as the Yarra Ranges, noise levels on the shortwave bands were quite manageable. At times, it might rise to perhaps an S3, but hanging a variety of antennas cut for a mix of bands and erected in different directions certainly allowed for some flexibility and control over the local man-made noise.

Previously, we lived in a highly urbanized environment where 24-hour S9 noise levels prohibited any SWL or Ham activity from home. But moving to more spacious living at Mount Evelyn allowed me to drag out the radios, string up those wire antennas and really enjoy again the hobby that was such a part of my youth.

But over the past 12 months, I have noticed an increase in local man-made noise around here. The level of general electrical hash on the bands has increased markedly. At certain times of the day, the S-meter is rising to between 5 and 7. And it is not always predictable when the noise levels will rise and fall.

A few weeks ago, the local electric company decided to do a major overhaul of some power poles and wires in an area not far from here. So, the entire region was without power for about seven hours. Fantastic, I thought! I’ll hook up the Yaesu FTDX3000 to the 12v sealed lead acid battery and do some daytime DXing right here in the shack in a totally noise-free environment. Once the lights went off, I fired up the rig and tuned the bands in search of weak signal DX delights.

Err….well, not to be! Indeed, the results were somewhat underwhelming! It was disappointing just how much man-made interference was evident on the shortwave bands, even though such a large area around Mount Evelyn was without power. The hash was still registering a steady 3 on the S-meter. Certainly, it was better than when the mains power is in regular operation. But in the past, when the power had been off, the noise dropped right away, and battery-powered DXing from the radio shack was a real pleasure. But alas, not on this occasion!

So, I began thinking about why this was so. What is going on here?[…]

Click here to read the full article at The Mount Evelyn DX Report. 

Spread the radio love

Can’t receive anything on your new shortwave radio–? Read this.

This morning, I received a question from Andrew, an SWLing Post reader in the UK.  Andrew writes:

May I ask a question please? I am very much a newbie to this. I am not really interested in FM, but I would like to listen to international stations on SW, utilities stations, amateur broadcasts and if possible, local airports, aircraft on air band.

I have just purchased a Tecsun PL-680 and have tried it inside my home with the telescopic and wire aerial that came with it, plugged into the antenna port and clipped to a point near the ceiling. All inside the house and the wire aerial did improve the reception, but I get hardly and channels either during the day or night.

Grateful for your detailed advice on what I need to do exactly to improve the number of stations I can receive.

Kind regards
Andrew

Thank you for your question, Andrew, and I hope you don’t mind that I share it here on the SWLing Post as I receive this question so frequently from new shortwave radio enthusiasts.

Of course, a number of things could be affecting your shortwave radio reception and there is, of course, the possibility the receiver is faulty–however, this is very unlikely. Let’s talk about what is most likely the culprit:

Radio Frequency Interference (RFI)

RFI is quite often the elephant in the listening room. It’s not always immediately obvious–especially if you’re new to shortwave listening.

RFI (also known as QRM) is radio noise that is created locally and often concentrated in our homes and neighborhoods. RFI deafens our shortwave radios by overwhelming the receiver with strong spurious signals. Even if you can’t hear the noise, it could still be overwhelming your receiver from a different portion of the band.

RFI can emanate from most any modern electronic or digital device in your home: televisions, power supplies, dimmer switches, smart appliances, and even computer hard drives. Honestly, most any device could be the culprit.

These “Wall Wart” type adapters can create a lot of RFI

RFI can also be caused by power line noises outdoors which have a much larger noise footprint and typically require intervention from your local utilities company/municipality.

In all likelihood, though, it’s a noise inside your home.

There’s a quick way to determine if RFI is the culprit:

Take your radio outdoors, away from the noise

Depending on where you live, this might only require walking with your radio to the far end of your garden/yard, or it might require hopping in your car and visiting a local park. The idea is to find a spot far removed from houses and buildings, outdoor lighting, and even power lines if possible.

Once you find a listening spot, turn on your portable and tune through some of the popular shortwave radio bands.

If in the late afternoon or evening, I like tuning through either the 31 meter band (9,400–9,900 kHz), 41 meter band (7,200–7,450 kHz) and, if late evening, the 49 meter band (5,900–6,200 kHz). Jot down the frequencies where you hear stations and perhaps even make notes about the signal strength. Then go back home and see if you can receive as many stations. Shortwave stations change frequencies often, but if you listen from home at the same time the following evening, the radio landscape should be similar.

My guess is that you’ll hear many more stations in the field than you can from within your home.

Living with RFI

Sadly, RFI is just a fact of life in this century. It’s very hard to escape, especially for those of us living in dense urban areas. This is one of the reasons I’m such a big fan of taking radios to the field.

There are things you can do to improve reception and I would encourage you to read through this post from our archives (the first two points in the article directly address RFI). Do your best to track down sources of noise and eliminate them.

If you find that, even in the field, your shortwave receiver can’t receive stations with the antenna fully extended, then it may indeed be an issue with the radio itself and you might need to send it back to the manufacturer or retailer if it’s within the return window.

Post readers: If you have other suggestions, feel free to comment!


Do you enjoy the SWLing Post?

Please consider supporting us via Patreon or our Coffee Fund!

Your support makes articles like this one possible. Thank you!

Spread the radio love

Take the field and abandon the radio noise!

The most common complaint I hear from new SWLing Post readers is that they can’t hear stations from home on their receivers and transceivers. Nine times out of ten, it’s because their home environment is inundated with man-made electrical noises often referred to as QRM or RFI (radio frequency interference).

RFI can be debilitating. It doesn’t matter if you have a $20 portable radio or a $10,000 benchmark transceiver, noise will undermine both.

What can you do about it?

Since we like to play radio at home, we must find ways to mitigate it. A popular option is employing a good magnetic loop receive antenna (check out this article). Some readers find noise-cancelling DSP products (like those of bhi) helpful when paired with an appropriate antenna.

But the easiest way to deal with noise is to leave it behind.

Take your radio to a spot where man-made noises aren’t an issue.

Field radio

If you’ve been reading the SWLing Post for long, you’ll know how big of a fan I am of taking radios to the field–both transceivers and receivers. Not only do I love the great outdoors, but it’s the most effective way to leave RFI in the dust.

Sunday was a case in point (hence this post).

Let’s be clear: I blame Hazel…

Last week, I did a Parks on the Air (POTA) activation of Hampton Creek Cove State Natural Wildlife Area in Tennessee. It’s a beautiful area with a fantastic hiking trail (the Overmountain Victory Trail) in a relatively remote/rural area.

About 5 minutes before Hazel’s cow patty fun.

My family had a great time at the site–we enjoyed a picnic and I played radio–but Hazel (our trusty canine companion) decided to roll in a cow patty during our hike. Hazel thought it smelled wonderful. Her family? Much less so. And all five of us were staring at a two hour car ride together.

Fortunately, my wife had a bottle of bio-degradable soap we use while camping, so I washed Hazel in Hampton Creek. (Turns out, Hazel didn’t mind that nearly as much as getting washed at home in the tub.)

In all of the commotion I forgot to take my EFT Trail-Friendly antenna out of the tree. Doh!

The EFT Trail-Friendly antenna is incredibly compact and quite easy to deploy.

The EFT is my favorite field antenna for POTA activations. It works so well and is resonant on 40, 20 and 10 meters. With an ATU, I can also tune any bands in between. I’ve deployed this antenna at least 130 times in the field and it was still holding up.

I was bummed. Hampton Creek is nearly a four hour round-trip from my home. Was it worth the trip to rescue my antenna?

Fast-forward to Sunday: my amazing wife actually suggested we go back to Hampton Creek Cove on Sunday and also check out nearby Roan Mountain State Park. Would my antenna still be in the tree? Hopefully.

Whew! Still hanging out!

Fortunately, my antenna was still hanging there in the tree as I left it the week before. I was a little concerned the BNC end of the antenna may have gotten wet, but it was okay.

Mercy, mercy, so little noise…

I turned on my Elecraft KX2 and plugged in the antenna. Oddly, there was very little increase in the noise level after plugging in the antenna. That worried me–perhaps the antenna got wet after all? I visually inspected the antenna, then pressed the “tune” button on the KX2 and got a 1.4:1 SWR reading. Then I tuned around the 40 meter band and heard numerous loud stations.

What was so surprising was how quiet the band was that day (this time of year the 40M band is plagued with static crashes from thunderstorms).

Also, there were no man-made electrical noises to be heard.  This allowed my receiver to actually do its job. It was such a pleasure to operate Sunday–no listening fatigue at all. Later on, we set up at Roan Mountain State Park and did an activation there as well. Again, without any semblance of RFI.

When I’m in the field with conditions like this, I always tune around and listen to HF broadcast stations for a bit as well. It’s amazing how well weak signals pop out when the noise floor is so incredibly low.

It takes ten or so minutes to set up my POTA station in the field, but if you have a portable shortwave radio, it takes no time at all. None. Just extend the telescoping antenna and turn on the radio.

Or in the case of the Panny RF-2200 use its steerable ferrite bar antenna!

If you’re battling radio interference at home, I would encourage you to survey your local area and find a noise-free spot to play radio. It could be a park, or it could be a parking lot. It could even be a corner of your property. Simply take a portable radio outside and roam around until you find a peaceful spot with low-noise conditions. It’s the most cost-effective way to fight RFI!

Post readers: Do you have a favorite field radio spot? Do you have a favorite field radio? Please comment!

Also, check out these articles:

Spread the radio love

Secure federal facility interfering with garage door openers?

Many thanks to SWLing Post contributor, Jakon Hays, who shares a link to the following article at Inside NOVA:

A top-secret and secure federal government facility just northwest of Warrenton admitted this week it may be responsible for crippling dozens of garage door openers in two nearby subdivisions, FauquierNow.com’s Don Del Ross writes.

More than 70 Olde Gold Cup and Silver Cup Estates homeowners have reported that openers started to fail about two weeks ago, according to Betty Compton, Olde Gold Cup’s Neighborhood Watch group coordinator.

Warrenton Training Center B, a classified federal facility, issued a statement this week saying its radios may be to blame.[…]

Click here to read the full article.

This is interesting. I’ve heard this is a very common complaint in/around large broadcast facilities. Whether or not it’s always true is up for debate, but I should think it would be easy to test the RF environment in the area and confirm.

Spread the radio love