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Banana Skins – November 2018 (#123-131)

123. Police radios can trigger positive breath test

If you’re ever asked to do a breath test by the police you might do well to insist that they turn off their radios before you blow into their breathalyser. The advice comes from an ex-copper who wrote to us after we printed a story about police concerns about interference from next-generation handsets (see above – editor). He writes: “When at the Metropolitan Police training school, it was taught that PCs should not press the PTT (push to talk) button on the personal radio whilst waiting the requisite forty seconds for the lights to (hopefully) go red. Never. “Oh, no – indeed. Definitely not. Especially if the subject was being ‘griefy’. Honest.”

He adds that the idea that that a PC might surreptitiously give a quick burst of transmit on his radio whilst his partner was administering the breath test to an uncooperative suspect, was similarly frowned upon. Its worth noting here that, at least in Britain, the actual charging and conviction of drink driver suspects relies on a different test which is administered at police station. Our correspondent explains the technique was used to annoy awkward customers. “This merely gave the opportunity to cause inconvenience, spend time filling out the forms, apologise profusely and sincerely (again, honest) afterwards, give the driver back the keys to his car and advise him where he might find a cab to drive him back to it. At four in the morning. “Oh dear. Terribly sorry, but we are not insured to give you a lift if you are not a prisoner anymore. Sir. No cash on you, then it’s a long walk back, in the rain,” he added.

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Another reader, who worked for the St. John Ambulance, a first-aid volunteer service, recounts a time on duty when he saw a policeman using his radio to trigger a positive result on a breath test. Apparently it was all a bit of innocent fun and the guy was using the trick in a rather strange attempt to chat up a woman he fancied. Our man in the St. John’s Ambulance service says that ambulance radios can have the same effects on breathalysers. It’s not that we condone drink drivers, but if you’re ever pulled up (and assuming you’re not too drunk in the first place) now you know what to look out for. Lets be careful out there.

(Article by John Leyden in The Register,, posted on the 26th January 01, sent in by Graham Eckersall, G4HFG.)

Pacemaker users get digital radio warning

A reader was taken aback when he took delivery of digital radio handset from Motorola that contained a series of warnings for pacemaker users. The Motorola d700 handsets, which will be used in a Terrestrial Trunk Radio (TETRA) digital communications project, contain recommendations from the Health Industry Manufacturers Association which advise a minimum separation of 15cm between a handset and a pacemaker.

This advice, albeit well intentioned, leads to a number of surprising tips. Pacemaker users should not keep handsets in their breast pockets and furthermore should “use the ear opposite the pacemaker to minimise the potential for interference”. It goes on: “if you have any reason to suspect that interference is taking place” with a pacemaker you should “turn the handset OFF immediately” — that’s if you’ve not been hit by shortness of breath, of course. We gather there’s also warnings about hearing aids, “other medical devices”, explosives, and a range of other things, which leads our reader to conclude that “it’s hardly surprising people are scared of these things”.

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A health and safety expert at Motorola confirmed the information and pointed out, quite reasonably, that the instructions are part of the training it provides its users to make sure its equipment is used safely. He said that “similar power levels” were used by Tetra and GSM equipment, which means that interference levels were “not horrifically different”, though higher, than older analogue technologies commonly in use today by emergency services, the chief market for Tetra.

So, should pacemaker users avoid mobile phones? Well the issue seems to have more to do with the electrical immunity, or lack of it, associated with a particular pacemaker whose manufacturers ought to provide concerned users with all the information they need. It makes you think though.

(Article by John Leyden in The Register,, posted on 5th March 01, sent in by Graham Eckersall, G4HFG.)

People around the globe are fascinated with Bremerton’s tale of a bizarre electronic failure

The widespread failure of keyless remote entries on vehicles around Bremerton last week has sparked interest far beyond the local community — thanks to the ubiquity of the World Wide Web and nationally syndicated talk radio. Since the story first ran Saturday in The Sun, it has been broadcast by two nationwide radio programs that focus on bizarre phenomena — “Coast to Coast with Art Bell” and “The Jeff Rense Show.” It also has been posted on numerous Web sites, including The Sun’s, and reprinted in other newspapers.

The widespread posting has fuelled a flood of responses from all over the country — and even from as far away as Russia and Croatia. Meanwhile, the strange incident remains a hot topic in West Sound as residents try to solve the mystery and add to the list of impacts beyond the mass failure of remote entry devices. The outage, which went from about 4 p.m. March 21 until about 6:30 a.m. Monday, apparently was caused by interference with the short-range UHF radio signals transmitted by small hand-held keyless remote devices to an unlocking receiver in the vehicle.

The source of that interference remains a mystery, however. The Federal Communication Commission believes the local military presence is “very possibly” the source of the disruption, said a government official familiar with the agency’s investigation into the outage. Although Navy officials still insist they can find no link between the interference and USS Carl Vinson’s recent return to Bremerton, most responses sent to The Sun reflect a widespread belief that the military presence is to blame for the disruption. They also question whether the interference might have caused other problems — and that still might be occurring.

Some samples of responses:

  • An ex-Navy technician wrote: “You know as well as I do that an active electronic countermeasures (ECM) was inadvertently left aboard a ship docked at the shipyard, causing remote car lock devices to be inoperative. That’s what ‘jammers’ are supposed to do. It is not a coincidence that the effect occurred when (USS) Carl Vinson arrived, and then when the sailors went back to the ship Monday and took a good look around, they turned it off.”
  • A computer buff in Izakovic, Croatia, wrote that electromagnetic emissions from U.S. Navy warships fry his Internet modem whenever they pull into the local harbor. He now is on his fourth modem and suspects that similar emissions caused the interference in the Bremerton area. “Bremerton mystery is not a mystery at all. U.S. Navy has in operation VTRPE radar and IR/visual/radar satellite detection shielding technology (which causes the problem).”
  • Two Bremerton readers reported that something has been interfering periodically with the radio signal that controls their household atomic clocks. The clocks display the exact time, as broadcast continually over several radio frequencies between 2.5 and 20 MHz from a transmitter in Colorado that is linked to the U.S. Naval Observatory’s atomic clock. One clock owner said the problem has persisted intermittently even after the keyless remotes began working again Monday.

Other readers reported problems with TV reception, car alarms and computer microchips in Bremerton and Port Orchard last week during the period of disruption.

  • Employees of state and local government agencies reported that their radio systems experience periodic failures in the Bremerton and Bangor areas. “We’ve called (PSNS), and they won’t tell us one way or the other,” one respondent wrote via e-mail. “If we knew when they were testing it would help.”
  • A respondent who identified himself as a “Russian geophysicist” sent an e-mail from Moscow suggesting other possible sources of the disruption, such as rogue TV signals or police communications gear.

(Article by Lloyd A. Pritchett, The SUN newspaper of Bremerton, Wash. USA, March 2001, sent in by Graham Eckersall, G4HFG, who saw it referred to in the ARRL news (US ham radio organisation) in April 01.)

Mobile phones can trigger remote-controlled explosives

In the corner of the town square, four GIs huddle behind a wall. Someone yells: “Incoming!” A huge explosion lifts the ground, raining down heavy clods or earth that hurt if you don’t turn your back. “Glad I moved you up?” smirks the director, Tony To, having advised a more sheltered vantage point than that previously adopted. The crew set up for the next shot. A warning: mobile phones off. Incoming calls can trigger remote-controlled explosives.

(Extracted from an article by Jeff Dawson, in the Sunday Times TV and Radio Guide, 13th May 01, page 4. Jeff was watching a programme about the second world war being made.)

Two lightning incidents

After a lightning strike to a factory, a servo-operated packaging machine was found to be operating backwards. It continued to operate at full speed even when its guards were opened, despite supposedly having a hard-wired safety system.

(Contributor wishes to remain anonymous, May 01.)

Late last year, lightning struck in the car park area of a UK Building Society’s town centre headquarters. Large voltage surges knocked out the security cameras, and were transmitted to other electronic equipment in three buildings via the connecting cables. Once they had entered the building’s electrical systems, the voltage surges damaged the security system, fire alarm and distributed computer equipment.

Latent damage was also caused to the interface between the fire alarm and the radio tag-operated automatic door system, but this went unnoticed at the time. The problem was identified only when a fire alarm went off some weeks later and staff were unable to exit through the automatic doors. Fortunately it was a false alarm.

(Taken from “Don’t lose your data in a flash” by Tony Harrison, Electrical Review, Vol. 227 No 12, 10-30 June 94, page 90,

The indications are that lightning strikes are on the rise in Europe.

And it can be expected that damage from these strikes will also be on the rise.

(Taken from “Markets for Power Line Surge Suppressors in Europe” by Christopher Lanfear, PCIM Europe, Nov 2000, Page 34.)

 Seven EMI incidents reported by Dag Björklöf

Today we can easily find examples of more or less serious electromagnetic problems:

  • The magnetic field caused by ground currents in the water pipe system makes it impossible to use sensitive electronic instruments in part of a hospital building.
  • A patient-coupled infusion pump is damaged by electro-static discharge, but thankfully the alarm system is not affected, and a nurse is alerted.
  • An operation using a plastic welding machine cause interference with a patient monitoring and control system; the monitor fails to detect that circulation has stopped in the patient’s arm, which later has to be amputated.
  • A wheelchair carrying a handicapped man goes out of control when it comes close to a radio station antenna mast, and eventually the occupant is ejected into the street.
  • A robot starts running amok due to a radio control transmitter, smashing all equipment within its reach. (Editor’s note: always make sure the mains isolation switch for a robot is outside its possible reach!)
  • Interference from a passing truck with a radio transmitter causes a crane to drop its load on a person.
  • A passenger’s laptop causes a plane’s navigation system to malfunction, causing the aircraft to go off course.

(Taken from “Immunity testing: Examining requirements and test methods” by Dag Björklöf, Compliance Engineering European Edition’s 1999 Annual Reference Guide, page 51.)

Illegal CB transmitters on trucks

Radiocommunication Agency (RA) officials obtained convictions against truck drivers for using illegal citizens band (CB) radios. The convictions came as a result of an official stake out of two truck stops on the M4 highway in Wiltshire, U.K., last October.

(Taken from: “Enforcement Efforts Around the World” Conformity 2001 Annual Guide, page 209.) (Editor’s note: Almost certainly these truckers were using illegal high-power boosters, capable of creating very high field strengths over large distances. Not a good idea when incidents such as described in the 6th bullet of No. 129 above can occur.)

Bluetooth and Wi-Fi can interfere with each other

The co-existence of Bluetooth and Wi-Fi in the 2.4GHz Industrial Scientific and Medical (ISM) band was discussed at the recent Wireless Symposium in San Jose. Because the simultaneous operation of these two systems can interfere with each other, the search is on for ways to improve their performance when they are in proximity.

As explained by Jim Lansford of Mobilian Corp. (Hillsboro, OR), these two technologies (known as WPAN and WLAN) are headed for significant growth. “Co-existence has become a significant topic of analysis and discussion throughout the industry”, says Lansford. “With both of them expecting rapid growth, co-location of Bluetooth and Wi-Fi devices will become increasingly likely.” “They create in-band coloured noise for one another. Neither was designed with specific mechanisms to combat the interference from the other. Bluetooth assumes it will hop away from bad channels. WLAN (802.11b) assumes that if it fails, two Wi-Fi stations tried to transmit at the same time.”

(Extracted from “Living in a Wireless World” by Sherrie Steward, Compliance Engineering, March/April 2001, page 10.)

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.

We are proud to carry on the tradition of sharing Banana Skins for the purpose of promoting education for EMI/EMC engineers.

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