Banana Skins – July 2019 (#198-204)

198.  Fluorescent lamp interferes strongly with AM and FM radio

Was just at a cheesy hotel with the replacement circular fluorescent lamps directly above (2 feet) the hotel-provided radio (less cheesy than most). Turning on the light completely destroyed the signal. AM and FM and all channels. Turn it off and the radio was nice and clear. Wanted to steal the bulb to measure later – decided on the towels instead. Not only should these bulbs have not been CE marked, they should have had a label for use only inside microwave ovens or something.

(From Gary McInturff, 24th April 02, in a thread on “CE for Fluorescent Lamps” on the IEEE’s emc-pstc discussion list.)


199. 
CE marked keyboard fails ESD tests

Well, I’ve stumbled over one of my pet peeves again. We had a combination keyboard/touchpad (CE marked) which failed ESD testing a couple of months ago. It would either give false inputs or become unresponsive when 8KV air discharges were made to the touchpad. I tried ferrites at both ends of the cable…no luck. Since we don’t make the keyboard, I can’t open it up and make changes (although I would like to open it up with a sledgehammer…that would make some changes).

So, we bought another brand.  This one has a keyboard and trackball. Our hope was that the trackball would be more zap-proof than the touch pad….No dice…snap, crackle, pop it fails too. Oh, by the way, this keyboard was prominently CE marked as well.

(From Chris Maxwell, 19th April 2002, in a thread on “Suitable CDN for IEC61000-4-6 ethernet 10/100” on the IEEE’s emc-pstc discussion list.)


200. 
The most spectacular ‘banana skin’ of all times!

In 1899 (!) in Colorado Springs Nikola Tesla himself tested his tesla coil.

He did not use filters, the harmonics burned out the wiring in the power company in Colorado Springs.

(We like to celebrate each 100th Banana Skin with a funny or off-beat item. This one was sent in by Geert Starre on the 14th May 2002.)


201. 
Potential safety implications of mobile phones and aircraft, with examples

Please could you help with a project I have, investigating potential safety implications of mobile phones and aircraft. Three potential hazards come to mind.

While using mobile phones on the ground, whilst refuelling the aircraft, the displacement of air at a rate of approx. 1500 lt. per minute out of the tanks as vapour spill from vents at the wing tips. They are not intrinsically safe, so what energy is required to ignite fuel vapour? (I have personal experience of seeing the results of a person with a mobile phone strapped to his belt while filling his petrol tank. The mobile rang, igniting the vapour, and causing a jet bast from the tank which unfortunately took all the skin off from his wrist to his elbow).

Batteries should one become damaged and or shorted causing a fire what would be the possible fire hazard and what extinguishant should be used?

Potentially the worst case scenario RF break through from the mobile into the systems. They often can be heard over radios when transmitting in the vicinity of the receiver, a unwanted signal in my view, therefore what could happen if the signal is induced into and reacted upon in one of the many other systems? Again personal experience has shown of signals in an industrial process line where a 3 watt transceiver was being used some 15 meters from a large electronic motor control center, which sent motors into random speeds simultaneously causing major stoppages for the process line and months of these random transients to get solved. From an aircraft’s point of view I have experienced transmitting from the aircraft’s fitted VHF Transmitter on a particular frequency and the aircraft pitching nose down some 20deg while the autopilot was being used.

(A query made by Paul Barnes to an IIE Special Interest Group on the 2nd February 2002.)


202. 
Vacuum cleaner interferes with computer terminals

One of my first business trips after I got out of college was going to Chemical Bank in New York City, because one of the Sycor 250 terminals (for which I had written the firmware) would lock up every night.  The hardware designer and I installed some hardware and software monitors on this unit, and left for the evening.  Next morning we returned, and discovered that it had died shortly after 11pm– the very time that the cleaning people were making their rounds!

We discovered that the cleaning people were plugging their industrial vacuum cleaners into the same wall outlet as our terminal because it was convenient.  I think that the bank changed to a simplex wall outlet there, and that solved the problem.

(John Barnes, dBi Corporation, from a thread entitled Re: Voltage Spikes on Power Lines etc on emc-pstc on 14/03/02 23:14:43, http://www.dbicorporation.com.)


203. 
Indoor equipment needs to withstand 6kV spikes on the mains, for reliability

I discuss problems with powerline-spikes in chapter 8, Designing Power Supplies, of my book    Electronic System Design: Interference and Noise Control Techniques (Prentice-Hall, 1987, now out of print).

For equipment that will be used indoors, you should try to design your equipment to be immune to 6kV spikes.  That is approximately the voltage at which our wall outlets arc over.

(John Barnes, from the same thread as item 202 above)


204. 
Tracing aviation frequency interference in Miami to illegal cordless telephones

The Enforcement Bureau of the FCC is taking strong action against retailers who are illegally marketing non-compliant equipment, specifically long-range cordless telephones. The Commission has initiated action against New Image Electronics (NIE), a Miami, Florida electronics store, for selling long-range cordless phones designed to operate on civil aviation frequencies.

The agency’s action followed a six month investigation that began in February, 2001 when the FCC’s Enforcement Bureau received reports from the Federal Aviation Administration (FAA) of sporadic, but potentially harmful, interference to aviation frequencies in the Miami area. FCC agents traced the interference to NIE, and

investigators visited the store on at least two separate occasions, actually purchasing a long-range cordless telephone during its second visit. Not surprisingly, the purchased phone possessed none of the labelling or FCC authorization required for marketing the device in the United States.

In its response to the Commission, NIE did not deny that it had sold the phone to the FCC’s agents, but claimed in its defense that their clerk had mistakenly believed that the phone was being sold for export when one of the agents gave his address as “Puerto Rico.” In its forfeiture decision, the FCC noted that Puerto Rico is part of the United States.

The Federal Communications Commission (FCC) has also taken action against two other Miami-based retailers for illegally selling long-distance cordless telephones. The Commission has issued monetary forfeitures to Electronics Unlimited and Lightning Electronics for the illegal marketing of non-compliant, high-powered cordless phones.

(From Curtis-Straus Update for April 2002, via Conformity Magazine.)


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: https://www.emcstandards.co.uk/emi-stories, 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.

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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