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Banana Skins – May 2019 (#180-187)

180.  Locked BMW interferes with digital TV

Question: When my BMW 330Ci is locked, it causes interference to my digital TV service – despite being parked about 30ft from the dish. My wife’s Mercedes-Benz doesn’t cause this, no matter where it is parked. I was thinking of swapping her Merc for an X5, but two BMWs parked on the drive at once might limit my evening’s entertainment to Scrabble. I’m sure I could get the dish moved, at a cost, but I shouldn’t need to do that. I.B., via email.

Reply: There is an EC directive about electronic interference that came into force several years ago. Either your car’s alarm immobiliser system or the dish/TV receiver does not conform to it.

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VSWR and its Effects on Power Amplifiers

Voltage Standing Wave Ratio results from an impedance mismatch between a source (an amplifier) and a load (test application). This mismatch can influence the performance of the source.

(Honest John’s Agony column, Daily Telegraph Motoring Section, Saturday 30/03/2002, page 10,

Two navy warships nearly collided when the radar of one disabled the steering of another

The minehunter HMAS Huon went out of control and veered across the bow of the frigate HMAS Anzac. Huon – the first of six state-of-the-art coastal minehunters – lost its steering as a result of electromagnetic interference (EMI) from Anzac and passed ahead of the frigate “at close range” according to an Auditor-General’s report last week. The previously unreported incident occurred in June 2000 while the warships were sailing to Singapore.

The near-collision was used in the Australian National Audit Office report to highlight shortcomings in the testing and evaluation of new defence equipment, especially in the navy, leading to the installation of only partially tested systems. “The incident prompts questions concerning the adequacy of EMI testing during developmental testing and evaluation and whether the services should complete more extensive operational testing and evaluation before integrating new platforms into defence exercises,” the report stated.

The ANAO report rejected Defence Department claims that such testing was expensive and not necessarily cost-effective and said that T&E (testing and evaluation) should be conducted as early as possible in order that risks could be reduced before they became dangerous. “In extreme cases, inadequate T&E could have tragic consequences,” the report said.

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(Extracted from “Loose radar blips nearly sink ships” by Wayne Smith, The Courier Mail (Brisbane, Queensland, Australia) Friday February 1st 2002, sent in by Chris Zombolas of EMC Technologies Pty Ltd, Melbourne, Australia, March 2002,

Experiences of interference in U.S. residential environments

Currently, appliances in the U.S. do not need to meet any EMC compliance standards. Since U.S. appliance manufacturers can (and do) produce domestically used products without any regard for EMI suppression, how serious is the EMC problem in the U.S.? It’s difficult to know the entire scope of the problem, but a few examples have come to our attention. For example, the new 2.4GHz portable phones will not function near laundry rooms when certain models of washing machines are running. This problem is easily overcome by not using these portables near these washers. A little inconvenient, but not intolerable.

In another case, a company that imports and distributes microwave ovens asked us to investigate complaints that some of their microwave ovens were turning on by themselves. The cause was a surge on the power line, probably caused by the air conditioning system turning on. The solution was not simple and required units to be recalled and fitted with a hardware and software modification. The costly remedy was necessary because, in this case, the susceptibility of the appliance electronics created a safety hazard.

In Europe, EMC issues will continue to be managed through the existing EMC Directive, so European manufacturers will remain quite familiar with designing and developing next-generation products that are EMC compliant. Without such a directive here, U.S. manufacturers will need to institute good EMC practices to ensure a more EMC friendly environment for smart, networked appliances.

(Extracted from “Smart Appliances and EMC – Good EMC practices necessary to prevent smart homes from being chaotic homes” by Nissen Isakov, president of LCR Electronics, Norristown, Pa. USA, writing in Appliance Manufacturer magazine, March 2002 issue, pages 16-17.)

Examples of interference problems with automobiles

More electronics means more risk from externally generated electromagnetic interference (EMI) and from EMI generated by systems in the vehicle that are adjacent or interconnected. The effects can be quite serious: on certain highway overpasses in Europe, the engines of some vehicles have been shut off when their control units encountered high EMI levels from, among other things, high-voltage lines beneath the roadway, reported David Ladd. He is communications manager at Siemens VDO Automotive (Auburn Hills, Mich., USA), which operates an electromagnetic compliance testing lab. “These problems must be identified and corrected before the vehicle goes into production,” he emphasized.

Because of these risks, the auto industry is re-evaluating its requirements and testing for new sources of EMI. Suppliers are increasingly relied upon to develop expertise in managing potential risks during the early stages of engine control unit development, noted Ladd. And the growing use of optical-fibre databuses is eliminating one possible source of EMI problems.

(Extracted from “Can you trust your car?” by Ivan Berger, Contributing Editor, IEEE Spectrum, April 2002, pp41-45.)

CB radio used to intentionally jam early electronic ignition systems

It reminds me of a weakness of the original Bosch “Jetronic” electronic injection system as used as OEM equipment on various European cars in the late 1960s to mid 1970s (this was at a time when the good ol’ carburetted American V8 was still the norm here).

A common stunt was that people with (illegal) 50 Watt transmitter boosters attached to their CB radio, would drive up beside a Bosch-injected VW or Volvo or whatever, toot the horn to get the driver’s attention, then hold up the CB’s microphone for the guy to see, and (with a flourish) key the transmitter. The injection system in the “victim’s” car would immediately stop and his car would die until the transmitter was keyed off! Now, THAT’S EMI susceptibility!

(Extracted from a posting on in the thread: “RE: Automotive standards” by Bob Wilson of Vancouver, 5th April 2002.)

5.  Magnetic fields near to mains transformers

Take a large poorly built transformer or solenoid and push the core hard up against the equipment housing and you could well exceed 0.7mT nearby. Several metres from a train (0.7mT) is less likely but not impossible. These figures should be borne in mind the next time you read about the dangers of the magnetic fields from overhead power lines. I have several times seen building site welders sitting on their transformers with their testicles dangling over the gap and I haven’t seen welders dropping like flies.

(Extracted from a posting on in the thread: “RE: Teslars??” by Nick Rouse, 8th February 2002.)

NASA report on aviation incidents involving passenger electronic devices (PEDs)

NASA runs an Aviation Safety Reporting System (ASRS) to which pilots and other aircrew can voluntarily report incidents. On 1st May 2002 they released a report of 50 incidents taken from the ASRS which involve the use of Passenger Electronic Devices (PEDs), but not all of the reported incidents concern electromagnetic interference.

This report is very useful when you need to show people that some PEDs can interfere with some aircraft systems and communications.

(From Gary Fenical of Laird Technologies, USA,

One of the aviation incidents reported in the NASA ASRS PED report (see item 186 above)…

Aircraft: DC9. While at cruise FLT FL3100 we noted the onset of multiple anomalies with independent and interrelated onboard electronic systems. The radar altimeter began flagging and sweeping, the GPWS and TASCII annunciated ‘FAIL’, the VORS flagged, despite good idents and, by and large, rational signals.

Tests of the equip were otherwise satisfactory so we made announcements requesting that certain PEDs (cellphones, pagers, TVs and radios) be verified in a depowered condition, and the flight attendants did a ‘PED Walk’ in the cabin. The problems initially vanished but then reappeared, and we repeated the process this time requesting that all PEDs be depowered.

The 3rd and final PED walk revealed that several pagers had to be depowered by battery removal, and there was a computer in use with an external battery pack. (No incoming calls to pagers were admitted to.) After this, the anomalous indication vanished for good and all systems operated normally (including the GND VOT signals).

The regular “Banana Skins” column was published in the EMC Journal, starting in January 1998. Alan E. Hutley, a prominent member of the electronics community, distinguished publisher of the EMC Journal, founder of the EMCIA EMC Industry Association and the EMCUK Exhibition & Conference, has graciously given his permission for In Compliance to republish this reader-favorite column.

The Banana Skin columns were compiled by Keith Armstrong, of Cherry Clough Consultants Ltd, from items he found in various publications, and anecdotes and links sent in by the many fans
of the column. All of the EMC Journal columns are available at:, indexed both by application and type of EM disturbance, and new ones have recently begun being added. Keith has also given his permission for these stories to be shared through In Compliance as a service to the worldwide EMC community.

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