Man-made pollution of radio spectrum is a growing problem

January 28th, 2016, Published in Articles: EngineerIT

Man-made pollution of the radio spectrum is a growing problem for everyone, with radio amateurs being the first to notice its effects. The main reason is that radio amateurs work mostly with low power transmissions and weak signals which are particularly susceptible to man-made noise.

PLT Pilot installation at Rooiwal, Tshwane . It did provide broadband but also severe unintended radio spectrum pollution

PLT pilot installation at Rooiwal, Tshwane. It provided broadband but also severe unintended radio spectrum pollution.

In a recent editorial, Dave Sumner, CEO of the American Radio Relay League, used an interesting analogy to draw attention to the problem. “Do you know how to boil a frog? Assuming you ever want to, toss the frog into a pot of boiling water. The frog will simply jump out and if quick enough will be none the worse off. But if you put the frog in lukewarm water and slowly raise the temperature it will go to sleep before it knows what is happening. There are many analogies to the story of the frog including radio spectrum pollution,” he wrote in QST of December 2015.

Often the source of radio interference is from unintentional emitters, devices that radiate radio frequency (RF) energy even though their operation does not require it. In the USA, Europe and to a lesser extent in South Africa, powerline telecommunication (PLT), also referred as broadband over powerline (BPL), is a typical example of spectrum pollution. Anyone with a basic understanding of what happens when you put RF energy on an unshielded, unbalanced conductor and who is not blinded by the political pressure or greed could see from the outset that it was a terrible idea.

The City of Tshwane is a good example of how they believed PLT would provide inexpensive broadband to the masses. The South African Radio League (SARL) actively opposed the idea and canvassed against it. After a lot of testing and observation of a pilot network in an outlying residential area of Tshwane, common sense prevailed and the city dropped the idea. Tshwane ultimately opted for a WiFi network that is currently providing free internet access in parts of the city with plans to extend it.

For several years the Independent Communications Authoity of South Africa (ICASA) worked with industry and the South African Bureau of Standards (SABS) to develop regulations for PLT but after several drafts the project appears to have been abandoned. Interestingly in the last draft guideline for PLT, the system was not permitted in coastal towns to prevent possible interference to the marine radio service.

PLT is still used in a product called “homeplug”, providing broadband connections inside a residence or office. The SARL is keeping a close watch on this as it could be a contributor to an increased noise floor level.

All radio communication services are negatively affected by spectrum pollution, but radio amateurs are usually the first to notice. Dave Sumner used another analogy in his article. “Like miners’ canaries, the caged birds were taken down mine shafts and their distress or death warned of the presence of lethal gasses. But unlike the luckless canaries, we do not have to submit quietly to our fate.”

In most cases the sources of spectrum pollution are well-known, like arcing from powerlines which pre-existed radio but is still a source of RF interference often found in older suburbs with overhead mains feeds where aging insulators are arcing over and generate strong RF fields. More recent sources of spectrum pollution are variable speed motors in home appliances and industrial equipment, solar controllers and inverters, unshielded data network cables and switch mode power supplies.

Another growing source of interference are energy efficient LED light bulbs. None of these should cause radio spectrum pollution if they are well-designed and properly installed. But not every light bulb on the market is well-designed and meets the required standards. Competition in the market pushes manufacturers to take short cuts to keep their prices down.

Another growing problem is that although the first products coming onto the market are tested and comply with the standards for RF interference, later batches do not always comply. In some recent cases in the USA, it was found that the spaces on the printed circuit board for RF suppression were not populated.

Another major problem in South Africa is load controllers. While the first units installed met the specification for RF inference and carry the type approved ICASA label, later batches do not meet the required specification and are causing havoc in the radio spectrum. The SARL is working with ICASA in an effort to resolve the problem but in the first instance, local municipalities should act on interference complaints and not hide behind the type approved ICASA label. They should take responsibility and not install these units until they have solved the RF pollution their units are causing. Similar problems exist with electric fencing and gate motors when not properly installed with RF suppression and are extreme polluters of the RF spectrum. Standards exist but enforcement is not at the level it should be.

While radio amateurs may be the first group to notice and report spectrum pollution, other users of the radio spectrum should become more aware of the problem. The same RF interference also deafens their radio receivers and could well pose a threat to safety and security.

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