Banana Skins – July 2021 (#342-346)

342. Spectrum reallocation to reduce interference with emergency services radiocomms 

26 January 2005: Philadelphia FOP Wants Radios Replaced; failures characterized as possible life-or-death issue. In a follow-up to a story reported earlier on Interference Technology’s website, major news outlets in the Philadelphia metropolitan area report that the head of the city’s Fraternal Order of Police (FOP) has called on city officials to replace the two-and-a-half-year-old Motorola police radio system because of repeated communications failures. A report from an independent consulting firm hired by the city cited possible interference from wireless telecoms Nextel Communications and Cingular Wireless. City officials expressed reluctance to scrap the $52 million dollar system and expressed hope that the FCC’s proposed spectrum-swap for Nextel would help alleviate the problem. Meanwhile, FOP officials warned that their next press conference could bring very tragic and sobering news if the problems go uncorrected. 

11 February 2005: Nextel, FCC Agree to Spectrum Swap to Solve Long-Standing Interference Issues. In an historic agreement, Nextel Communications will receive a new swath of spectrum from the FCC in exchange for ceding its former spectrum in the 800-MHz band. Nextel will also pay to reconfigure the airwaves it currently occupies. Presumably, this pact will put an end to the complaints from numerous public safety agencies that Nextel’s signals interfere with and sometimes drown out vital police and fire radio communications. The agreement was announced by FCC Chairman Michael Powell and Nextel President Tim Donohue. Powell hailed the solution to a problem that he termed, “difficult, complex, and challenging.” Donohue characterized the resolution as, “simply the right thing to do for first responders, homeland security, and for Nextel.” 

Specifically, Nextel will move its remaining spectrum in the 800-MHz band, bundle it together, and move it further away from the airwaves used for public safety broadcasts. The public safety broadcasters will be located next to each other within the band. Nextel will also receive new spectrum in the 1.9-GHz band, where other major wireless telecoms are located. The new spectrum is valued at $4.8 billion, which Nextel must pay the FCC; but the telecom will receive a $2 billion credit for the spectrum it is returning. Nextel will also receive a credit for the relocation costs it incurs; these costs have been estimated at $1.3 billion. The transition is to begin immediately and should be completed in about three years. For the official announcement, go to http://www.fcc.gov. 

(From Interference Technology E-News, 26 January 2005 and 11 February 2005. For the background to this issue see Banana Skin No. 281.)

343. ‘Broadband over power line’ (PLC) will interfere with radio astronomy

Sharing studies between the radio astronomy telescopes and the power line communication systems in the HF region. Summary: Radio Astronomy has frequency allocations in 13.36-13.41 MHz and 25.55-25.67 MHz on a primary basis worldwide. These bands are extensively used by radio astronomers to observe electromagnetic waves emitted by the Sun, the Jupiter and other large, gaseous planets in the solar system. The powers from a single Power Line Communication (PLC) system in the above radio astronomy bands are -33 dBW and -29.2 dBW respectively and therefore the PLC systems seem to be a harmful interference source for the radio astronomical observation in the HF band. 

It is necessary to keep an adequate separation distance to avoid harmful interference to the radio astronomy telescope, and we calculated the separation distance based on the free-propagation method. We obtained a value of 424 km. If the PLC system is widely deployed, it is sure that the interference level increase greatly and the separation distance will become much larger. Thus it was recognized that it is quite difficult to share frequencies with the PLC systems and radio astronomy telescopes, at least, in Japan, and that a new technology to dramatically reduce leaked emissions from the power lines are crucial for the PLC systems to coexist with other radiocommunications services. Authors: by M.Ohishi, J.Nakajima and M.Tokumaru 

(The above was extracted from: http://www.arrl.org, June 2003. Concerned radio astronomers should also see Banana Skin No. 272.)

344. Interference from lighting is an ever-increasing threat

Standard CISPR15 (EN 55015) is a special product family standard for electrical lighting and similar equipment that has served the market well for many years, but in recent times the incidence of interference from lighting has increased [1]. This has coincided with technological developments in the lighting industry [2]. With the increasing pressure for more energy efficient lighting [3] and because of requirements for more energy labeling of household lamps [4], there will be an increase in the use of technologically advanced lighting. This is the reason, why CISPR15 has been seen to be insufficient and it is under revision.

Unlike the generic standards and most other product family standards, CISPR15:2000 contains no requirements for radiated emissions from 30MHz to 1GHz. Also in Finland, it has been found that some lighting appliances are causing harmful interference to radio communications on the VHF band. Therefore these lamps and luminaires are not in compliance with the EMC Directive (EMCD), although they might fulfil the requirements of CISPR15.

Energy saving lamps (ESLs) are typical sources of interference to TV VHF broadcast receivers and also to private radiotelephone networks on the VHF band [2], [1]. Finnish EMC market surveillance authorities, the Safety Technology Authority (TUKES) and the Finish Communications Regulatory Authority (FICORA) have received several interference complaints concerning ESL bulbs. In 2003, FICORA solved ten interference cases caused by ESLs. It is likely that these kinds of interference cases will increase in future. Fig. 1 shows the measurement results from an ESL that was intended to be used in a new conference hall in Tampere, Finland. These kinds of lamps were installed throughout the building. Radiated interference from these lamps was so high that it was not possible to use VHF radiotelephones inside. All ESLs were then replaced. The bandwidth of the interference was about 50MHz (-30 dBc points) and the interference occurred on the frequency band 159 – 209 MHz. In Finland, this band is sued by many different radio services including emergency services (police, fire brigade, ambulance services, etc.).

TUKES has also received other complaints concerning interference cases caused by ESLs. Typical equipment being disturbed has been, for example, the remote control of TVs or narrow band in-house telecommunication networks using domestic 50Hz/230V electricity mains wiring. The disturbances between TVs and their remote control equipment was mostly caused on the infrared band, for which there are no requirements at all. In local telecommunication cases, conducted EMI from ESLs made it unable to use domestic electricity wiring as media for signal transmission. Also, other fluorescent lamps have caused both kinds of disturbance.

Finnish market surveillance test results with regard to ESLs have been a little better than those from Germany. According to Finnish tests, 43% of ESLs do not fulfil the standard. In Germany, 48% has failed. In ten cases, emissions from ESLs were so high that TUKES was obliged to restrict the distribution of the lamps (sales bans). Surprisingly, defects were found to be equally distributed between inexpensive and expensive ELS models.

Also in the USA, surprisingly high conducted emissions from some ESLs have been measured in the band 450kHz to 2MHz. The need for measuring was prompted by problems with AM radio reception while ESLs were in operation, and levels approaching 100dBµV occurred at the low end of the MF band. At 1.7MHz, the levels were more reasonable, but were still in the region of 70dBµV. The majority were reported as very high-order harmonics of the supply frequency, which suggest that the rectifier should have had shunt capacitors and/or soft recovery diodes. If these emission levels are common, where does that leave the troublesome subject of power line communication? It seems to both provide a case for relaxed limits and an indication that communication may be compromised by the very emissions that support that case! [6]

As serious problem seems to be that the ESLS originating from the Far East do not have uniform quality and quality can vary a lot between production runs. The high number of lamp and luminaire manufacturers in the Far East leads to competition between factories. There is a ready buyers market and factories are prepared to do nearly anything in order to keep their clients satisfied. It became apparent from project interviews that the importer himself could mar the quality of products e.g. through over negotiating the price down too much. 

An open European market makes the importation business easy. It also tempts unskilled businessmen with dreams of big profits, and they usually make so-called ‘one-off’ business deals. They import a few containers of products from the Far East, distribute them quickly on the market, and then disappear. Such kinds of business change the price structure of the market, which impedes the operations of those importers who take care of their reputations by being responsible businesspersons.

The most troublesome interference case in Finland concerning metal halide lamps (MHLs), occurred in relation to a public swimming pool. The rated life time of the type of MHLs used was 10,000 hours usage, but after 2,000 hours, the sparking interferences of the lamp’s electrodes during normal operation caused serious interference to TV receivers in a neighboring house. When the lamps were exchanged for new ones, the event repeated itself after about 2,000 hours. One regrettable detail was that the pool had to be once again emptied before it was possible to change the lamps.

In Finland, there has been one very serious interference case caused by a single rechargeable torch model. After about half a year’s use the regulatory circuit together with the battery began to oscillate causing serious interference to one TV channel. Before identification of this problem source, many interference cases were noted all around Finland. In fact, this could be considered to be more of a battery-charger problem than a lighting interference one.

The four halogen sets we tested in 2002, fulfilled all the other testing, but they had enormous difficulties with mains harmonic currents. According to measurements made by the Swedish Authority, halogen lighting sets powered by an ‘electronic transformer’ might cause radiated interferences. Also, [2] supports Swedish views. It seems that almost all plasma lights do not fulfil the requirements for conducted emissions. However, they have not yet caused serious EMC problems in Finland.

(Extracts from “Lighting Interferences – An Ever Increasing Threat!” by Jyri Rjamäki, IEEE 2005 International EMC Symposium, Chicago, Aug 8-12, ISBN: 0-78-03-9380-5, pp 7-12. For more instances of interference from lamps and luminaires, see Banana Skins 19, 40, 58, 102, 158, 159, 171, 198, 218, 271 and 322.)

345. Rice cooker interferes with pacemaker, plus other examples of interference

This is an excerpt from a monthly newsletter that sends out interesting news items. I don’t believe this is an April Fools’ item, but then who knows? A Japanese woman’s automatic rice cooker changed the settings on her pacemaker. Doctors doing a routine check up were baffled to find that the hi-tech pumping device they had implanted in the woman, 60, had been remotely adjusted. They contacted the manufacturer, who visited her home and found that a rogue rice cooker had somehow beamed signals to the device.

[Source: A&A Economic Digest – April 2003 Edition, 1 April 2003] [Quite plausible, in light of previous reported cases of electromagnetic interference on pacemakers]

From ACM Software Engineering Notes back issues:

  • Arthritis-therapy microwaves set pacemaker to 214, killed patient (S 5 1)
  • Retail-store anti-theft device reset pacemaker, man died (S 10 2, 11 1)
  • Pacemaker locked up when being adjusted by doctor (S 11 1)
  • Electrocauterizer disrupts pacemaker (S 20 1:20)

And from RISKS:

  • Stores’ shoplifting gates can set off pacemakers, defibrillator (RISKS-20.05)
  • Heart pacemaker and implantable cardioverter defibrillator recalls and alerts involve 520,000 devices (S 26 6:8, RISKS-21.60)

(Sent in by Simon Brown, who saw it on the RISKS-LIST: Risks-Forum Digest  Friday 4 April 2003  Volume 22 : Issue 67, FORUM ON RISKS TO THE PUBLIC IN COMPUTERS AND RELATED SYSTEMS (comp.risks), ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator. Archived at http://catless.ncl.ac.uk/Risks/22.67.html.)

346. Lightning strikes are a major cause of insurance claims in the U.K.

It is true that you are unlikely to be struck by lightning in the UK. But it may come as a surprise to know that around one-third of all insurance payments made by UK household insurers are compensation for damage caused by lightning strikes. Most of the damage is not caused by the direct strikes, but by the effects of more distant strikes. These produce voltage surges, most often on the mains electricity supplies, but also sometimes in telephone lines and other long cables. 

(Taken from “When Lightning Strikesby Jim O’Connor in Electrical Engineering magazine September 2005, page 27, http://www.connectingindustry.com.) 

About The Author

Keith Armstrong

After working as an electronic designer, then project manager and design department manager, Keith started Cherry Clough Consultants in 1990 to help companies reduce financial risks and project timescales through the use of proven good EMC engineering practices. Over the last 20 years, Keith has presented many papers, demonstrations, and training courses on good EMC engineering techniques and on EMC for Functional Safety, worldwide, and also written very many articles on these topics. He chairs the IET’s Working Group on EMC for Functional Safety, and is the UK Government’s appointed expert to the IEC committees working on 61000-1-2 (EMC & Functional Safety), 60601-1-2 (EMC for Medical Devices), and 61000-6-7 (Generic standard on EMC & Functional Safety).

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