The EMI - RFI page

December 2010. Over the years I have pinpointed many, many RFI-sources. They blocked my reception on the low bands as well as on the higher HF bands.
Electromagnetic interference (EMI, also called radio frequency interference - RFI) is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source (from Wikipedia). Often these interference sources are occupying a large part of the frequency spectrum. This can occur on LF, HF even into VHF and UHF. On many occasions, these interference sources are due to an electrical malfunction. This can be hazardous and possibly result in fire. Many buildings have been destroyed due to electrical malfunctions. Keep this in mind when you track and locate an RFI source, it can help you to convince the owner of a building or specific equipment that you are actually helping him (in most cases you are!).

This page will address the accounts of RFI sources that have been located over the years. Pictures, audio files, movies and stories will give an idea on what kind of problems can be encountered..

How do you locate an RFI source with simple means? Second half of the nineties, I started getting serious about locating RFI sources. I use beverage antennas (8 in total, every 45 degrees) and as such I have a pretty good idea from which direction an interference source is coming. When on higher frequencies, I use a yagi antenna to pinpoint the exact heading. Then I take a look on a military detailed map of my neighborhood and put out a line to follow in order to track down the interference. Nowadays it is even easier with web-based tools such as Google Earth and the like, to have a look in which area you must conduct your search.
Note: if you encounter RFI on the low bands and do not have directional RX antennas to pinpoint the RFI-heading, go up in frequency and see if you can find the same RFI on the higher bands (listen on AM mode). If the same RFI is audible on the higher bands, and if you have a yagi antenna, proceed as follows. Point the yagi to where the RFI is strongest (and confirm by turning the yagi 180 degrees that the RFI is much weaker or not even audible anymore in that heading - after this check, turn back to the strongest RFI heading). Turn the yagi (several times, for accuracy) left and right, away from the strongest RFI heading, looking for two RFI-points of equal minimal strength. Once both these points are determined, one can calculate the exact heading of the RFI noise source.
(e.g. if you find these RFI minimal strength points to be at 120 and 300 degrees, the RFI-source will be at 30 (or 210) degrees)

The maximum distance for an interference source so far has been 2 km. The easiest way for RFI-hunting is to walk or take your bike. Some probably have direction finding equipment in their car, I don't but often use the car to get closer to the RFI-source and then walk.
At first, I was using a small portable AM radio with LW/MW frequency range. This type of radio is useful when the interference is continuous over a large part of the radiospectrum. The stronger the signal gets, the closer you are, simple eh? With the ferrite antenna inside this type of radio, you get some directivity. Once you get used to how this works, it will be a bit easier to pinpoint the interference quicker.
Some RFI-types however, are not broad range but rather repeat every 15 or 20 kHz or so (frequency controlled devices, wall wart type power supplies etc.). For this you will need a receiver with exact frequency readout. I use a Yaesu FT-817ND for this purpose. Non-hams should be able to find small receivers (I have a Sony ICF-PRO80, which I still use for tracking RFI). On the low frequency bands 80 and 160m, I often use ARDF (Amateur Radio Direction Finding) fox-hunting equipment, which is very small to carry and very directional.
I prefer to listen in AM mode, rather than SSB or CW, as most of the times RFI sounds more distinctive in this mode.

The ARRL used to maintain a page with many soundrecordings of different types of RFI (page originally produced by Ken VE3HLS). The ARRL is currently working on a new web page to be released early 2011.
Do you experience interference and you are not sure what it is? Check out the old ARRL page (web archive), perhaps you'll find what it is (not all audiolinks are active, unfortunately):
For general and more specific information on RFI, check out the main RFI page of ARRL:
Update 8 March 2017: John WA7UAR was so kind to direct me to the current ARRL page with soundrecordings of RFI sources:

IARU Region 1 Monitoring System has a page with lots of soundfiles on it: (not all RFI related, but certainly interesting).

Jim Brown, K9YC, made an extensive, excellent 66 page article on the subject of RFI A Ham's Guide To RFI, Ferrites, Baluns, And Audio Interfacing from the perspective of the mechanisms that cause the RFI and couple it in and out of devices and systems.

Chuck Counselman, W1HIS has written down excellent suggestions for RF noise mitigation in his 42 page article entitled "Common-Mode Chokes", which is available on the Web at

Chris G3SOW has written down his own memorable RFI-hunting experiences, at the other end of the HF spectrum on the 6 meter band. It makes for some great reading:

Next follow my own experiences. Good luck in hunting down RFI! Oh yes, one final piece of advice: always stay cool when approaching people to inform them about RFI originating from their house/company. And before you knock at the door, BE 100% SURE it is the correct door you knock at!

A picture of some of the equipment used to locate RFI-sources. Left hand, an ARDF tracking device for 160m band. Right hand, the SONY ICF-PRO80 receiver.

The OVERVIEW picture
Click on the picture to get a geopgraphical overview of most of the following cases.

It is striking that 11 cases are effectively related to (dangerous) electrical anomalies. Mostly found in businesses (restaurants, shops,...), not in ordinary household homes.

This is one of the first cases I solved. Heavy interference, I couldn't hear weak signals anymore. I went out for a walk with my first ever RFI-detector, a simple AM radio which my grandmother used in her kitchen when I was a kid. My walk with the radio brought me to a famous restaurant (distance 180 meter), harbored in an old restaurated farm built in 1719. I talked to the waiter, a young guy. I told him about a radio interference I picked up, and it seemed to come from the rain gutter of the house. Eh? Well yes, the rain gutter. He took a ladder and we went for the rain gutter (click on the picture to the left). I let him listen to the interference. Okay, he said, let me see. Up he went. In order to get from the ladder up the tiny platform leading to the external airconditioner and other equipment, he reached for the rain gutter to use as a support. As soon as he touched the gutter, he got an electrical shock, shouted in pain, and instantly the interference on the radio stopped! Back down from the ladder, still shaking, he asked me if this problem could be connected to the problem of electrical shocks they got from time to time in the kitchen, when touching the sink or fridge...
I told him it most probably was related, and probably due to a poor and/or incorrect grounding. He went to call for the electrician next, after thanking me for warning them (and for the electrical shock, hi). A pretty dangerous case closed.

'In Europe the CE marking (also known as CE mark - comes from 'Communauté Européenne') is a mandatory conformance mark on many products placed on the single market in the European Economic Area (EEA). The CE marking certifies that a product has met EU consumer safety, health or environmental requirements. By affixing the CE marking to a product, the manufacturer – on his sole responsibility – declares that it meets EU safety, health and environmental requirements.'

One day I experienced a terrible interference on the 80m band. I went for a walk with my grandmother's AM transistor radio. The RFI seemed to come from the house of the neighbors across the street (distance 65 meter). The neighbor and I used to live and play in the same street when we were kids... it sure is a small world. Upon further investigation in the house, the RFI was pinpointed to a series of halogen lamps on the 1st floor hallway and in two bedrooms, eight (or was it ten?) in total. I took one out of the ceiling, and noticed suspicious 'electronic transformers without brand name' were attached to all of the lamps. I then contacted the company who installed these lightings (10 years prior), and later paid them a visit. I took one of the units along, they didn't recognize it but admitted they must have installed it (10 years is a long time in construction business). They offered me conventional transformers to replace the electronic transformers, at a discount price. After installation, the RFI was gone.

Moral of this one: if the EU lets manufacturers 'affix' CE marking to their products, without any controlling body monitoring/testing their products, things like these 'unbranded electronic transformers' come on the market and can cause havoc. NOT a good idea. In the past 'experiments' like this had to pass technical scrutiny, nowadays anyone can so to speak put a CE marking on his product, without it really being compliant.

I received an interesting e-mail from Terrence WN4ISX on the subject of halogen lamps and arcing. Learned something new here, tnx Terrence!
Chuck W1HIS reacted to Terrence's e-mail, and sent me the article 'EMI Hall of Shame Begins – Halogen Lamp' he wrote for the Technical Correspondence in QST, May 2005. The ARRL kindly granted permission to post the article here.

The faulty CEILING LAMP cases
This is another early RFI case I solved. My JA beverage suffered severe RFI. I hit the road on my bike, carrying ARDF equipment. After a while, I found the culprit. It turned out to be a faulty ceiling lamp inside a sports store (a couple of hundred Watts halogen lamp, if I recall well).
At night I could clearly see a continuous blue arc in the defective lamp. This is dangerous stuff. These lamps tend to be left operational day and night, and in such a case this arc may very well turn the place into a fire. This has happened way too many times in such stores. McDonald's, Blokker, etc., they all have stores burned to the ground because of this kind of anomaly. If you are interested in the arc subject, here is a good article.
Click on the picture to the left to see the distance from my beverage antenna, 1 km.
During this bike ride, I also discovered at the same location a streetside faulty neon light for this store (and two other stores, a grouped store neon light). And farther away a faulty neon light at a butchery store ('Butchery' on the Overview picture).
The multitude of cases got a bit overwhelming in my early days of RFI-hunting, I called upon the services of our national Telecom service, who found my observations to be correct. They informed the store managers and butcher and requested them to get the anomalies rectified by an electrician. They did, case solved.

Years after, October 2005, I had a similar case in the WNW heading, also about 1 km away ('Ceiling Lamp 2' on the Overview picture).
I informed the store manager, who called for an electrician to replace the lamp. The store manager sent me a customer gift afterwards, nice!

The case of 'Tavern ALBATROS'
This case proves once more that electricity needs to be treated with appropriate respect.
Severe RFI on the lowbands in the NNW heading. I was still chasing Alaska and Hawaii on topband, this RFI needed to be put to a halt. I had a pretty good idea where to start looking, and in those days (this must have been around 2001, haven't noted it down) I was using the SONY ICF-PRO80 receiver as my main companion during RFI hunting.
So it happened I was walking up and down the famous national route (see 'The Latoya nightclub incident'), and kept on returning in the vicinity of this bar-tavern Albatros. It was pitch black outside, but the street lighting made sure the customers could see me walk back and forth, with a strange device in my hand and a headset, well, eh, on my head.
So finally in I went, followed by many curious eyes when I approached the counter. Behind it was a friendly, elderly lady. I explained her the reason of my visit, and let her listen to the interference on my radio. I told her this interference was possibly connected to some electrical anomaly, which could eventually result in a fire.
Her eyes went wide open and she almost shouted that she already had had a case of fire in the circuit breaker cabinet. She showed me the cabinet, indeed many black scorches were testimony to the fact that she had been lucky that the place hadn't gone up in flames before.
Now I got her complete attention and cooperation. She told one of the regulars to go around with me in the place and see if we could find something. Soon after, we discovered a faulty light switch on a wooden stairway. This was a very old installation, a loose wire arcing inside the switch on bare wood, this was asking for a disaster to happen.
The lady was very happy with my visit and thanked me for preventing a possible fire.
I think she retired, as in 2009 the Albatros was torn down to the ground, and has been replaced by a new business complex.

The case of 'Restaurant DEN KASTAAR'
October 2005, severe RFI on my west beverage antenna on the 80m band. This called for action. By now my bicycle had turned into a real RFI-hunting unit. A Sony ICF-PRO80 receiver, the Yaesu FT-817ND, a telescopic multi-band antenna attached to the bike, 80m ARDF equipment, in short, the lot.
My search brought me to a cosy little restaurant Den Kastaar, at a distance of 1.5 km as the crow flies. Waw, this interference was loud at my place, what could this be? I picked a quiet moment to talk to the chef. Tried to explain this technical matter to him, hmm, not so easy. Where did I live? Could he see my ID-card? Sure, I showed him and then he loosened up a bit.
The interference was not active when I talked to him, so we agreed I would call by phone when it was on. Long story short. It appeared to be their son's switching power supply to his computer screen. I talked to the son by phone, he told me he had noticed the power supply got really, really hot lately. Well, something was cooking inside, that was obvious. The son went for another power supply, case closed (and no fire!). I took the XYL for dinner to Den Kastaar one evening, we had a lovely meal and the sympathy of the owners.
So, what has the picture to the left to do with this story? Nothing really, except that I couldn't find a picture of the restaurant on the internet, and found this one of a Belgian beer I didn't know yet. Santé!
(oh yes, when I first found this RFI-source, I continued my homebound bike ride via another road, still listening to my ICF-PRO80. Lo and behold, I found another interference source, the WNW heading faulty ceiling lamp of the Ceiling Lamp cases!)

The 'AL BUNDY' case
Shoestores. No more, please. It took me two years to solve this one. The RFI was caused by a defective high voltage part of neon lighting at a shoestore. This company was not very cooperative in trying to solve this particular case of RFI, carrying a potential risk of a fire hazard.
I had to call upon the services of our national Telecom services, their antennas are visible on the picture to the left, while taking measurements at my QTH. Here and here are some more pictures of their antennas, situated at the shoestore's side.
The shoestore in the end had to rectify the dangerous situation, it took way too long for them to do so (end of 2005 to end of 2007!). It appeared to be a fault in the high voltage part of their neon lighting sign.
is how the RFI sounded like. It took out the whole 80m band. A second and longer soundclip is available, on which the RFI is much less distinct in strength than the interference on the first clip. That is because when the lighting was switched on, it took a while for the 'sparks' to get completely active (and become more dangerous in regard to fire hazard).
With special thanks to our Telecom services for a job well done to bring this case to a good end.

February 2007. A terrible interference on the west beverage, low bands. I asked Karel ON5TN (he's currently - December 2010 - active from Antarctica as OR4TN) if he was in for some RFI-hunting. Nothing to do on a Friday evening, so there we went.
After some walking around with our ARDF fox-hunting equipment, we stopped at the Latoya nightclub (distance: 1.5 km). This club is situated at a national route, famous for its brothels. My local ham friends following my RFI-hunting adventures, were waiting for this day to happen...all these green and red flickering neon lights, surely on4ww one day would have the luck of catching a faulty neon sign at a brothel, right?
Anyhow, they can keep grinning until that day happens, the Latoya nightclub is still one category away...
'Karel, you will stand guard here at the street side. If I don't return in 10 minutes, call 911'. 'Ok, but hurry up, will you, this place gives me the creeps!'. Well, this is a place you do not enter by merely opening the door. I rang the bell, and smiled in the camera. The door unlocked automatically. I entered a dark and small hallway. A few meters further, there was a heavy curtain. I pushed it aside and entered a sparsely lit bar, lounge/disco type. Few men, the older type, and even fewer girls, the younger type. And a bartender. That was my man! In the noise (music) I tried to explain what I came for. Not quite what he expected, I imagine. We went outside, much to the relief of Karel...
When we first arrived at the club, Karel had spotted sparks flying around at a broken section of the green neon lighting on the roof. We showed it to the bartender, a smart looking young man. He told us the neon lighting got dammaged in a storm some weeks before. He already had called for the neon-company to come over and repair the dammaged section, but they were not responding. I gave him the address of an alternate company (which I looked up during the 'Al Bundy' case - it was the same neon-company that did the installation, and they were also not responding to Al Bundy's call for a repair!). He then asked us if this interference he could hear on our radio, could be at the base of the interference he got on the sound/music installation of the nightclub. Told you, he was a smart looking young man, and he made a correct assumption-deduction!
This anomaly occured during the cold wet winter months, with sparks clearly visible on the roof. Had this happened during the previous hot summer, who knows what could have happened. Another fire prevented? Here is how it sounded like at a distance of 1.5 km.
Tnx Karel for your brave assistance! Can I call upon your services again 'when the national route real deal happens? Ye know, the red and green lights'?

The faulty FREQUENCY CONTROLLED DEVICE at a big sportscomplex
Half December 2009, a terrible interference popped up on my southwest beverage on the 160m band. It was snowing, freezing, no contests, so I decided to sweat it out a bit. On January 5th 2010 the interference was still around, and so was the frost. I took out my bike and RFI-hunting equipment, tucked myself in almost like an eskimo, and off I went. The interference was repeating every 15 kHz. I carefully tuned my analog fox hunting device to a frequency on which the RFI was noticeable. I took the small roads and zigzagged on the icy roads, one hand on the handlebar, one hand holding the ARDF-equipment, interesting exercise. Finally, half frozen, at a distance of 2 km I found the interference source to be in a big sportscomplex. I first talked to the housekeeper, who got me in touch with the maintenance person. No need to say I made a perfect entrance and quite an impression - half frozen, tucked in like an eskimo, with all kind of strange equipment attached to my body and bike ;-)
At first, not knowing who I was, understandably they told me to get in touch with the city council's responsible for technical matters. I contacted one of our club members, Bert ON4DMD who knows quite some people in that city's community, and then things started rolling and doors got opened. I spent a lot of time with the technicians, their manager. Also John ON4UN got along one evening, and we finally detected the culprit, a faulty frequency controlled device, steering a large heating system. It was not an easy exercise, the whole complex seemed to radiate RFI. The outer roof and walls are covered with large metal protection sheets. Talking about a big antenna, this building was one hell of an antenna re-radiating the unwanted signals of the RFI-source. Next follow the technical details.

Click here to view the video. First you will see and hear (AM mode) the Yaesu FT-817ND radio picking up the intermittent interference sound, while a relay clicks away in the background. After the camera zooms in on a relay; you can see the I/O switch rocking sideways (sorry for the blurred quality, the macro function was not enabled).
This interference sound was 2 kilometer away from my Beverage antenna, and loud! It was audible on 1816-1832-1845 kHz-etc. On this soundclip you can hear how it sounded at my station, at 2 km distance!
It took 3 evenings and a complete shutdown of the sports and cultural complex to locate this electrical malfunction. At first we thaught the industrial relay, labelled C5 on the picture to the left (click to enlarge) was at the origin of the RFI. However, once this relay was disabled, the RFI continued. It seemed the frequency controlled device that steers the large heating system of the sports hall, was at the basis of this anomaly, and this assumption was proven correct later on.
Notice the blue wire (relay point nr. 4) shows a shade of black, which may indicate this wire has heated in the past. Due to the malfunction of the frequency controlled device?
This picture, shows the 4 red leds (yellow circle nr. 1) and the green led (yellow circle nr. 2) that were all blinking on the rhythm of the faulty relay. Here is a video on which you can just see the green LED go off as the RFI stops.
Thanks to the very helpful crew at this facility for their friendly and professional conduct in order to help us locate this anomaly! Last week at a quizz in the sportscomplex (we did not do very well, tnx for asking) I met again with the friendly technician who was involved from the beginning of this case. He told me the company responsible for the heating system, replaced the faulty frequency controlled device. Case closed. Well, almost. The UBA, our national IARU organisation, will hold its annual congress in this sportscomplex, May 2010. The people of the complex already know who those ham radio operators are ;-)

Faulty streetlight

February 2010. John ON4UN calls me for an inteference source hampering his reception on the 160m band. It turned out to be a faulty street lamp. During the ignition startup sequence, RFI is strong. Once the lamp gets activated, the RFI disappears. There is an irregular pattern of this occurence, coming and going every few minutes. Ray, NR1R, gave me the following technical explanation on what is happening: the noise occurs when the sodium vapor start mecanism in the bulb starts arcing; when the sodium vapor electrode gets hot enough, the bulb lights and the noise goes away till the bulb goes dead again and the process begins again. It is called a cycling bulb. The bulb needs replacement when this occurs. Tnx Ray!
Here is a video on this type of interference. You will see the blue backlight of a Yaesu FT-817ND radio, the dimmed street light during interference sequence (ignition), and the disappearing of the interference once the lamp gets activated. Here is another video, taken inside John's shack. You can hear the interference on the K3 radio, and at the end it drops off (when the lamp gets activated). The radio is in AM mode.
The photo on the left shows the street lamp, with some of John's towers visible in the background. This photo shows the line of sight between towers and lamp (300m).
Remedy to this anomaly? Request the power utility to put in a new lamp. John has a red telephone line to that company. Over the years, we tracked down way too many of these faulty streetlight problems. And noisy high voltage agricultural electric fences... guess that comes with the luxury of living on the country side.

The tunnel case

The TUNNEL case
Truly, this was a difficult one. Late 2004, my reception towards JA on 160m was hampered by a barely noticeable raised noise level. Just enough noise, when intermixing with the ever so weak JA-signals, as to make it impossible to make out callsigns. Out came the bike (it seems I do more bike trips in winter than in summer) and with a 160m ARDF fox-hunting unit, I finally made it to 'the tunnel'. This is a rather big tunnel going under several railway tracks, at a distance of 1.8 km of our house. By sheer coincidence, at that moment I picked up the RFI caused by trains on my ARDF equipment at that location (going for one interference, pickin up another one) - more on trains later (the TRAIN case).
This RFI seemed to be coming from one side of the street, then from the other side. Strange. Well, it's much more fun doing this stuff in good company, so I called for John ON4UN and Marc ON4MA. Marc has a marine radio direction finding unit, it was time to put it to the test.
At first, we thought the RFI came from a light pole. We waited for darkness to arrive, put on our night camouflage colors, and opened up the small door at the bottom of the pole in order to get to the breaker switch (ye know, we're the 'don't do this at home' types). Ho ho, we noticed some nice sparking inside the pole near the breaker switch. Closed the door (yeah, well, we're not that daft), and called for the light pole maintenance crew. Case closed?
Not quite as yet. After the maintenance crew cleaned up the inside mess, the interference was still around. We got it wrong. Back with all the equipment, I started to suspect a certain house along the road (see picture to the left). I could not circumcircle the house, so I wasn't 100% sure and hesitant to knock at the door. Desperate, in the end I decided to give it a try. A young mother (with baby crying in background) opened the door. I briefly explained what I came for, if I could contact her husband? During a phonecall I explained to him what was going on. If we could meet? During my subsequent visit, it became apparent I picked out the right house. The good man was plumber by profession, and had homebrewed a frequency controlled central heating system. Obviously not according to standard. During another visit, John ON4UN brought along a filtering unit and grounding equipment. The good man promissed to install it, off we went and a while later the RFI was gone.
On this soundclip you hear me talking in Dutch, announcing the monitored frequencies on an AM receiver. In this order, you can hear the RFI on the following frequencies: 3.5 MHz, 1.8 MHz, 168 kHz and 7 MHz. In between 168kHz and 7MHz you can hear me cleaning my boots before re-entering the house.
Tnx John and Marc for your help!

The train case
The TRAIN case
Working on topband means working night shifts. And early morning shifts, just before the sun gets up. My first years with beverage antennas, opened up a whole new world. Not only in being able to work new ones, but in being able to detect all kind of man/machine made noises. The first beverage-years, I often noticed this annoying noise early in the morning. I couldn't pinpoint it, it came and went, on different headings. I listened often to this sound (in AM mode), and because of that, I immediately recognized the same sound while watching a train go by in 'The TUNNEL case'... mystery solved!
Here is a soundclip of a train passing by... at 1 km distance! Think I made this recording in AM mode, on CW it sounds not as distinct but is still pretty annoying. I can more or less follow the train on my beverages... usually starting on south heading, going over southeast and east, and finally disappearing on northeast.

January 2004. Now, this was a nasty one. In those days I was still chasing Worked All States on topband, and I got up almost every morning during the lowband seasons, October through March. And this for many years, before it finally happened tnx to KL7HBK on 17 October 2005. John was my last state, my last zone and a new entity, all at once, tnx John! Finally some more sleep during the winter seasons ;-)
And to say that ON4AOI worked his WAS in two weeks, early 2010! Now that is not fair...
What happened? I got up early in the morning(s), started calling CQ NA in the hope for a new one. All of a sudden a terrible noise comes on, for 10, 15, sometimes 30 seconds. What the heck is this now?
On February 20th I got so fed up with it, I took my bike and started a two person posse to try and find this little bastard. I positioned myself at 800m from our house, in the heading of where the noise was coming from. In my shack, Karel ON5TN came to rescue and informed me on 2m band when the noise was on (because of the very short time frames, it was very handy when Karel alerted me when the RFI started - I could stop the bike and start direction finding). After a while of trial and error, I arrived at a construction site, 1.6 km distance from our home. A big and deep pit, concrete pouring, construction workers running around. I rode back and forth, always getting back to this site, but not able to pinpoint the source.
I was standing across the street, when all of a sudden the noise came back. I took out my earphones, and could actually hear the same noise coming from across the street! And noticed it stopped when the construction crane stopped operating. Eureka!
I talked to the construction workers, later got in contact with the company selling these cranes. Two of its technicians came to the contruction site, where we had a meeting and did some tests with shielded cables and proper grounding, to no avail. John ON4UN then brought the company in contact with a professor at the University of Ghent, specialized in this matter (frequency controlled devices and RFI). He recommended acquiring specific filtering materials. Fast forward, June 2004. The company had not received the filtering materials yet, and priorities started shifting. October and December 2004, e-mails stay unanswered. End of December I make a phonecall to the contact person. He tells me he has been taken off the case and gives me the name of his successor. He also tells me he thinks no filters have been tested and no progress has been made. Restructuring in the company makes for different priorities. In March 2005 I detect RFI from a construction crane, from another manufacturer, at 2 km distance ('Construction Crane 2' on the Overview picture). October 2005, another crane from the first company gives me trouble.
John suggests I contact our national Telecom service for assistance in this particular case. By then, his radio reception also got hampered by a construction crane in his neighborhood. On 25 October 2005 we sent a detailed account of all facts to our national Telecom service. By the time their investigation got underway, unfortunately the involved construction cranes were dismantled. Case not really closed, as these types of cranes pop up on new construction sites ever so often.

Here is a soundclip of the first ever RFI-construction crane I encountered. You will understand that it is impossible to copy any weak signal on topband with this type of heavy interference. Distance from antenna to crane is 1.6 km.
Can it get worse? Here is a soundclip of two construction cranes hampering my reception on topband simultaneously!
The icing on the cake comes in this soundclip: a construction crane operational at 2 km distance and a train passing by at 1 km distance...all at once...wonderful!

Well, we can debate if this is RFI/EMI or not, but it sure makes a lot of noise. You can often hear this on yagi antennas, but also beverages are prone to it. Can be induced by snow, hail, even dry cold air. This kind of interference is one of Murphy's favorites during the CQWW contests... here is a soundclip.

The LED LIGHTING case at a Porsche garage
Aaah...the Porsche garage. Friendly and cooperative people. At a distance of 800m, two instances of RFI hampered my lowband reception. December 2009, I picked up this rather strong interference. As it was on my north beverage, it had to be on the (in)famous national route (see 'the Latoya nightclub incident'). I took the car this time, with all my gear inside. Took a walk and ended up at the showroom of a Porsche garage. Upon entrance and explanation to the employees, I was granted permission to walk around. The RFI was emanating from a circuit that was switched on at opening time, and switched off at closing time. It was just around closing time, so I could easily monitor which circuit was being switched off, one at a time. When finally the LED lighting at the computer desk was switched off, the RFI disappeared.
One of the employees told me they were not happy with the LED lighting (not adequately lighting their computer desk), and they already had called for the lighting company to make some changes in the near future. I sent this company twice an e-mail (March 2010) with detailed info on the problem, the e-mails stayed unanswered. I was going to call upon the services of our national Telecom service again if the problem was still around the next lowband season.
When I put up the beverages in October 2010, the problem was gone. This problem was most probably related to a 'dirty' power supply of the LED lighting. Our son recently installed two different LED lighting circuits in our living room. Two different power supplies, a good one, and a 'dirty' one giving loud interference on 160m band, but only audible on the Inverted-L antenna, not on the beverages. The RFI was weak because the electric cabling from the power supply to the LED lighting was very short. If the cabling had been longer (such as in the Porsche garage), the RFI would have been stronger and would be picked up by the beverages as well.

In 2005 during the CQWW CW contest, Murphy paid me a visit big time. I wrote a little story about it, still makes me smile. Just that weekend the Porsche garage had open door, showing the latest Porsche model. For this they probably worked together with Dior (customer gifts?) and a Dior neon sign was put outside, see picture to the left. I didn't record the RFI (if you read the story, you'll understand why), but it made a hell of a noise...what a weekend!
To top it off, in my search for the RFI caused by this neon sign I first knocked at the door of the company next door to the Porsche garage, MacNight, a bedding shop ('Airconditioner' on the Overview picture). Some terrible interference was picked up, it appeared to be a faulty airconditioning. The shop employee admitted the electrical household in the shop was a disaster. He disabled the breaker switch of that particular unit and would call for an electrician to have a look at it.

After reading Murphy's story again, I think I had better reserved a weekend at MacNight, sleeping all weekend long instead of playing the CQWW ;-)

This was an easy one. In 2003 I bought a couple of fluorescent tube lamps to be installed in my new shack. They are ignited with an electronic starter. On this video you can witness the result of a badly engineered fluorescent tube with electronic starter, causing heavy RFI on 28 MHz. Distance from the 28 MHz antenna to the lamp is 25 meter. If anyone has an easy solution for this one, let me know pse (yes, I know I should get a conventional starter).

The Samsung PLASMA TV case
For some years I had an annoying interference that was centered smack in the middle of the 80m (75m) SSB DX window. As I was not very active on 80m in those days, I didn't immediately tackle the problem. November 2004, it was time to take out the bike. I located the RFI source in a used car sales shop. The RFI was caused by a Samsung plasma TV, model P2. It was continuously on during daytime and late in the evenings. The RFI at 800m distance was noticeable at 200 kHz intervals. When close to the TV with a portable receiver, it was noticed that the TV radiated non-wanted signals from LF into VHF spectrum. Waw. The RFI on the soundclip, is recorded first on LSB, then AM mode, and back on LSB at a distance of 800m.
I first contacted Johan ON4IQ who was responsible for technical service at the TV cable company. At first I thought the RFI was originating from the cable company's outside distribution box near the street side. That box radiated terribly! Johan sent a technician, who changed an outside connector and inside the house another connector (there was no grounding at the TV side). This did not solve the problem. I then got in touch with Samsung, and after a lengthy process they replaced the P2 with a P3 model. They first sent a technician with another P2 model to our house, we installed it for a test setup, same problem. I then went to visit Samsung's technical facilities near Antwerp, where I 'sniffed' a P3 model with my Yaesy FT-817ND. The P3 model was clean! Bad engineering on the P2 model, but good and helpful response from Samsung!
In 2010 I got a Samsung LED TV myself, that one is clean. If it is good, we show it is a videoclip of my clean Samsung. See the text on Youtube for more details on this test.

Update January 2013 on my Samsung LED tv. This year-2010-unit is clean in that it does not generate RFI to my radio. However, I found out (tnx to my xyl) that my radio was interfering with the Samsung! On several bands (80-40-10m and probably other bands as well, not checked), the tv would switch on and off when transmitting. Also, the tv would every time go into DEMO (shop) MODE, and settings for the sound (Samsung sound when switching on/off) would be altered. Very annoying. I tried everything from putting ferrite onto the coax, power cord - disconnect peripheral cables (hdmi, etc.) - Corcom EMI filter. Nothing helped. Google came to rescue and I found a Dutch ham forum which described this exact problem (you can put it through a translate machine). It appears the touch switch panel at the front of the tv, is picking up RF and causing the mayhem. On this forum is described how to disconnect the touch switch panel circuitry by pulling out a connector. Problem fixed. As a result you can only 'talk to the tv' with your remote control. I am sure Samsung by now is aware of this problem. Another hiccup from the engineering department, which hopefully will be rectified in future models. Here is a photo page showing how I tackled this problem.

The Panasonic VIERA PLASMA TV case
Both my son (still living at home) and my closest neighbors have a Panasonic Viera plasma TV. This thing breathes RFI. In this video I use a Yaesu FT-817ND as receiver in AM mode, with a very insensitive telescopic antenna. The video starts with the tv switched off, and the receiver on 50 MHz. When the tv is switched on, you can clearly hear the interference come up. I then switch down in frequency: 28-24-21-18-14-10-7-3.5 and 1.8 MHz. Waw, this tv really radiates unwanted signals! When I switch channels on the tv, you can hear the RFI disappear in between channels, to come up again when the next channel pops up. At the lower frequencies of 3.5-1.8 MHz, I change the frequency a bit on the receiver to find the RFI. Apparently with the very insensitive antenna, only the stongest RFI signals are picked up. But mind you, with resonant outdoor antennas, you can hear the interference all over the radio spectrum. Bad engineering, Panasonic!
I know of other Belgian hams who have similar problems with this Panasonic Viera. In Germany, a court order forbid a neighbor of a ham to watch his Panasonic until the RFI has been cured. Way to go! Also in The Netherlands things are moving, and the national Dutch PTT has in cooperation with Panasonic replaced 'dirty' models by clean ones. Our national Telecom service has been asked to do the same, and I am confident they will.
In this video you can witness how the Panasonic sounds on 28 MHz. Receiver used is a Yaesu FT-1000mp in AM mode (preamp off).
The yagi antenna at first points in a direction where no RFI is picked up. While the yagi turns, you can hear the interference come up. I then sweep a bit over the 28 MHz spectrum, nice eh? At the end the antenna is turned away from the Panasonic (at 35 meter distance) and the RFI disappears.
Come on plasma TV engineers, you can do better!

The E-MAIL case
This is a truly intriguing and fascinating story.
On November 2, 2008, John G3PQA sent an e-mail to topband reflector about a new interference he experienced during the last month. His e-mail rang a bell with me. Together with Hugo ON7GB I had just started to investigate a very strong and annoying interference that blocked the 160m band. Could this be the same interference?
I got in contact with John, and we immediately started the posse. John brought along Paul G4PWA, Keith G3RPB and Ian G3NRW. On the Belgian side Marc ON4MA and John ON4UN completed the team.
It has to be said, the team went full speed and full force ahead to try and nail this border crossing interference. The CQWW contest was nearing, without a solution topband would be useless during the contest.
To show what is possible if a couple of like-minded hams get together, I put all e-mails chronologically in this .pdf file. In this 20 page document (yes, quite some e-mails went back and forth!), some hyperlinks to pictures, websites and soundfiles are included. Together with the e-mail content you'll get a good understanding of what was going on.

I was VERY eager to hit the road and do some direction finding on this RFI source. I had already driven 5 km in the neighborhood with my fox-hunting ARDF equipment prior to receiving John's e-mail of November 2, and it became obvious that it was not a local, but long distance RFI source. I was nearly on my way to Berlin, at one stage during the investigation!
Unfortunately I was plagued by a hernia at the time I wanted to go for 'the long distance hunt', and that may well be the reason we did not find the source. The RFI simply died between November 13 to 15. When I was finally able to go on a hunt on November 11, John ON4UN and myself went out with all sort of direction finding equipment. First stop was to be at ON7GB, who had the interference very strong on his TX-antennas. On the way to Hugo, we stopped at a McDonald's, took a bite, and to our surprise we kinda heard the RFI 'die'. It came back the following days, but more intermittently, to finally never come back. We had a nice visit at Hugo's place though, and that same day found an 80m RFI source near ON4UN's place!

What was it? We'll never know. Reviewing all the e-mails, I am convinced it originated in the vicinity of Antwerp. Too bad we didn't find it, would have been a great case to solve.
But it was a very gratifying experience to get an international group of hams working together in such a dedicated way. Ham Radio at its best? You bet!

The da-di da-di case (solar panel inverter)
Although this is not a typical RFI source, it can be very annoying and is indeed interfering when listening to weak signals on the 80m and 160m bands. A 10 second tone is followed by 7 seconds of two different alternating tones. These signals were first heard in 2009. ON4UN, ON4MA and myself can hear many of them in our neighborhoods. Over a period of 1 year, many more popped up. At one stage we believed it might be connected to more and more people watching digital TV. A settopbox? I had pinpointed one source already end of 2009, but didn't ring at the doorbell until 14 October 2011. Thanks to a very gentle and helpful houseowner, the real culprit has finally been determined. It has nothing to do with digital TV, it is all about solar panels. This signal is generated by an inverter manufactured by SMA Solar Technology (Germany) and distributed by Schüco Germany (model SB3000). The leads going up to the solar panels act as antenna and radiate the two-tone signal. I was planning to contact Schüco/SMA to see what possibly can be done about this, but don't have the time to invest in what possibly could be a lengthy correspondence process. Perhaps someone in Germany could approach them? It is clear that these devices are radiating signals that are not supposed to be radiated. Another possibility is that the signals are generated by another device in the electrical cabinet, and passed through the inverter, but this seems rather unlikely to me. This recording was made at a distance of 1 km. Some people may think it is the Hyperfix signal (heard in western Europe below 1825 kHz), it is not.

The automatic CLOTHES-MACHINE case (by Chuck W1HIS)
My automatic clothes-machine has a variable-speed motor drive that uses high-power solid-state electronic switching. L-C filtering of its 240-VAC, 60-Hz, power-line connection, and extensive ferrite-choking of cables inside and outside the machine, failed to reduce the RF noise level on the power wiring of my house. Of course the power wiring radiated....

By sniffing, I found a very high level of RF noise current on hot and cold water pipes throughout my house. These pipes radiated, too.
Inside the washing machine was an electric immersion heater, intended to increase the wash-water temperature if/when necessary. This heater was coupling RF noise from the electric wiring inside the machine to the water. Aggressive choking of the electric power wiring to this heater did not sufficiently reduce the noise current on my water pipes.

What did solve the problem was installing snap-on, split beads, of ferrite on the hoses that delivered hot and cold water to the machine.
The outsides of these hoses were covered by stainless-steel wire braid, for mechanical reinforcement. However, this wire braid was insulated at the washing-machine end of each hoses. It was water that carried RF noise current from inside the washing machine to each hose.
The braid aggravated my RFI problem by reducing the distance that noise current had to travel through water. After the noise current had emerged from the washing machine by conduction and displacement current through the water, it could continue essentially without loss as conduction current on the braid.

However, the wire braid exacerbated my RF noise problem more strongly by another, more subtle mechanism. The braid on the hot-water hose lightly touched the braid on the cold-water hose. This contact was a non-ohmic (nonlinear) conductor. The combination of (1) electronic-switching noise current from the washing machine and (2) current induced in my water pipes by powerful, MF and HF, AM broadcasting stations flowing through this nonlinear contact yielded intermodulation products that blanketed the MF and HF ham bands.

I eliminated this intermodulation by wrapping the cold-water hose with dielectric tape. I attenuated the electronic-switching noise current on the hoses further by connecting each of the wire braids to the metal body of the washing machine. One might might expect these connections to increase the RF noise current reaching my pipes; but they did the opposite. Via these connections the braid returned, to the washing machine, the displacement current due to capacitance between the water inside each hose and the braid on the outside. This solution addressed the essential problem, which had been that noise got out of the washing machine via the water.

The following photo shows how I connected the hose braids to the body of the washing machine.

The next photo shows how I sensed ("sniffed") the RF current in a hose. Noise current sensing is extremely important for understanding how noise power gets from a source to a conductor that's long enough to radiate it efficiently. Without such sensing, it's difficult to know how to solve a noise problem, and how effective a particular remedy is.

In the photo I am holding one side of a rectangular loop of insulated wire against the hot-water hose, near the end of the hose that connects to the hot-water supply pipe (where a shutoff valve has a red handle). The rectangular form is maintained by a sheet of cardboard, to whose perimeter the wire is fastened. Current flowing along the hose generates a B-field that encircles the hose and passes perpendicularly through the rectangular aperture of the loop. The flux of B through the loop generates an e.m.f., or "voltage," in the loop. At the lower right corner of the loop is a tiny gap, or "feedpoint," across which a coaxial cable is connected. This coaxial transmission-line carries the noise voltage to an HF receiver. The shield of this coax continues around the loop but does not bridge the tiny gap. Therefore, only the magnetic flux through the loop, and NOT stray electric fields (due, for example, to electric charges on my hand and the hose, contributes to the signal/noise seen by the receiver.

This rectangular, electrically shielded, B-field-sensing loop is highly specific. In the present case it is enabling me to distinguish between current in the hot-water hose, and current in the cold-water hose. In other situations, e.g., inside a washing machine or an electric power-distribution "load center" or "circuit-breaker panel," it enables me to see which of many wires/cables is carrying noise current. A whip antenna on a portable receiver, which responds to electric field, is MUCH less specific and much less useful. Its sensitivity pattern is not nearly so well defined, as one can deduce theoretically as well as empirically.

This loop is also useful for direction-finding in the far field (the radiation field, as opposed to the induction field) of a noise source. However, its sensitivity is relatively poor because it is not tuned, i.e., impedance-matched to the receiver. A tuned loop is better for DF'ing, unless the noise is very strong.

73 de Chuck W1HIS