Electromagnetic Interference
February 1966 Radio-Electronics

February 1966 Radio-Electronics [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

Fred Shunaman, Managing Editor of Radio-Electronics magazine, wrote the editorial column in this 1966 issue titled, "Electromagnetic Interference... The Future's Greatest Communication Problem." Boy, was his prediction right on the money. The ambient electromagnetic energy noise floor in the radio communications realm was many decibels below what it is today, particularly in urban areas, and Mr. Shunaman saw it coming; he just couldn't have known how intensely. Rural regions had practically no noise issues at the time other than interference with AM radios from dirty motor brushes, sparking transformers, and a few towers for local television and radio broadcasters. Nowadays, except for a very remote mountainous and desert areas, there is hardly a spot from where you cannot see a cellphone or microwave relay tower. Homes and businesses are filled with cellphones, computers, and "smart" devices spewing ISM band radiation. Wireless surveillance cameras are everywhere; your car or truck monitor every mile, and transmitters on your shopping cart tell the store where you are so they can text you with offers as you pass the shelf (having long ago learned your habits).

Electromagnetic Interference... The Future's Greatest Communication Problem.

Fred Shunaman, Managing Editor

The United States is the only civilized country that cannot legally restrain the manufacturer of equipment that will produce electronic interference. Our FCC can set the amount of radiation a uhf-TV tuner (for example) may produce. But it cannot prevent a manufacturer from making a TV set that produces more radiation. (The little notice you see on the back of the receiver is an indication of voluntary compliance. If a manufacturer does not wish to comply, he can construct a set with any radiation level he likes.)

But as soon as the set gets into a customer's hands and is put into operation, the FCC can seize the offending equipment and proceed against the owner, even to the point of levying fines and imprisonment.

This, of course, is nonsense. The place to stop trouble of this kind is at the source, not after a layman has bought in good faith what was sold to him as a perfectly legal piece of equipment. The FCC has requested Congress more than once to pass laws that would give it the power to stop the trouble at the source. Two bills (Senate 1015 and HR 564) that will give the FCC just that power have been introduced. Their way through Congress may be long and hard.

These bills would give the FCC authority to "prescribe the permissible degree of emission of radio-frequency energy of any devices capable of emitting radio frequency by radiation, conduction, or other means, in a great enough degree to harmfully interfere with radio communications." Radio and TV sets, electronic garage-door openers, electronic toys, electronic heaters, diathermy machines and welding equipment are among the things the FCC says can cause dangerous interference.

And interference can be dangerous. We have heard of devices (including portable FM receivers and garage-door openers - see p. 58) that interfere with aviation safety and which might cause a plane to crash. Rexford Daniels, president of Interference Consultants, Inc., tells of an electroencephalograph that was sending sane people to institutions because it was picking up signals from a freight elevator in the hospital and creating spurious brain waves. A story is told of a woman dispatcher in a taxicab company whose messages interfered with those used to control a guided missile. Her instructions to a cab driver actuated the destruct circuitry and blew up the missile.

Electromagnetic radiation can endanger human life and safety by interfering with communication. It can also be dangerous to human life and health by its direct biological effects, some understood, others probably yet unknown. We all know that direct exposure to powerful radar signals can have serious physical effects, possibly extending even to the second generation. We know less about the more selective effects of radiation at certain frequencies, although radio waves at 5 mc have been found to increase the size of tumors, and signals at 700 cycles can anesthetize the brain (Radio-Electronics, February 1965). The effect of radio broadcast signals on birds in foggy weather is another thing that is well known, and it has been pointed out that certain signals in the centimeter range can cause ants to line up with their antennae all oriented in the same direction.

Another radiation hazard, a little outside the field of radio communications, was reported recently in New York City. Fourteen children who had been watching steel girders being tested with high-voltage X-rays were rushed to the hospital and examined for radiation effects.

The Army took action against a station in Oakland, Calif., because signals from the station caused sparks in the equipment used to load and unload ammunition. An even more dramatic case was one in which a Navy plane touched off the whole stock of flash bulbs in a photographic store near where it was testing its radar.

This interference is curable. In many cases devices that are likely to produce trouble can be kept out of sensitive areas. In a research laboratory, for example, incandescent lamps can be used instead of fluorescent ones. Such things as radar transmitters can be confined to areas where they are not likely to cause trouble. (Citizens of the Pittsburgh suburb of Oakdale report that an Air Force radar unit in that thickly settled area produces beeps in radios, TV's, hi-fi equipment, electronic organs and public-address systems. These cannot be removed by any method of filtering, apparently.)

The second, possibly most important, remedy is to keep all undesired radio frequency inside the equipment. Amateurs have learned that it is quite possible to reduce harmonics of the operating frequency to an imperceptible level, and that direct radiation from the equipment itself can be cured by good shielding. Shielding has now become a science. We have louvers, screens and solid sheets especially designed to control radiation at various frequencies. We even have electromagnetic "weatherstripping" that will insure that the shielded back of a shielded cabinet, for instance, will make a perfect electrical connection when screwed on. (This has often not been the case in many "shielded rooms".)

We are continuing to use more and more power and to extend our signals over a wider range of frequencies at an increasingly greater rate. It is important not only that the FCC have the power to deal with all the known bad effects of electromagnetic radiation, but that we put in a great deal more time and effort searching out still unknown effects.