What
To Do if You Have an Electronic Interference Problem
This
is a self-help guide for the consumer published jointly by the American Radio
Relay League (ARRL), an organization representing Amateur Radio operators,
and the Consumer Electronics Association (CEA).
Introduction
As our lives become filled with more technology, the likelihood of unwanted
electronic interference increases. Every lamp dimmer, hair dryer, garage-door
opener, radio transmitter, microprocessor-controlled appliance or
remote-controlled new technical "toy" contributes to the electrical
noise around us. Many of these devices also "listen" to that
growing noise and may react unpredictably to their electronic neighbors.
Interference: What Is It?
Complex electronic circuitry is found in many devices used in the home. This
creates a vast interference potential that didn't exist in earlier, simpler
decades. Your own consumer electronics equipment can be a source of
interference, or can be susceptible to interference from a nearby noise
source. Interference can also result from the operation of nearby amateur,
citizens band, police, broadcast or television transmitters.
The term "interference" should be defined without emotion. To some
people, it implies action and intent. The statement, "You are
interfering with my television" sounds like an outright accusation. It
is better to define interference as any unwanted interaction between
electronic systems -period! No fault. No blame. It's just a condition.
Personalities
You can't overestimate the importance of personal diplomacy when you're trying
to solve a problem that involves two or more people! The way you react and
behave when you first discuss the problem with other individuals, such as a
neighbor, utility or cable company, or manufacturer, can set the tone for
everything that follows. Everyone who is involved in an interference problem
should remember that the best solutions are built on cooperation and trust.
This is a view shared by electronic equipment manufacturers, the Federal
Communications Commission (FCC) and the American Radio Relay League (ARRL).
Responsibilities
No amount of wishful thinking (or demands for the "other guy" to
solve the problem) will result in a cure for interference. Each individual
has a unique perspective on the situation --and a different degree of understanding
of the technical and personal issues involved. On the other hand, each person
may have certain responsibilities toward the other and should be prepared to
address those responsibilities fairly.
Any individual who operates a radio transmitter, either commercial or
private, is responsible for the proper operation of the radio station. All
radio transmitters or sources are regulated by the FCC. The station should be
properly designed and installed. It should have a good ground and use a
low-pass filter, if needed. If consumer electronics equipment at the station
is not suffering the effects of interference, you can be almost certain that
the problem does not involve the radio station or its operation. However, if
the interference is caused by a problem at the station, the operator must
eliminate the problem there.
Manufacturers of consumer electronics equipment are competing in a difficult
marketplace. To stay competitive, most of them place a high priority on
service and customer satisfaction. For example, many manufacturers have
service information that can be sent to a qualified service dealer. Most
manufacturers are willing to assist you in resolving interference problems
that involve their products. Over recent years, manufacturers have built up a
good track record designing equipment that functions well in most
electrically noisy environments.
The FCC will do what it can to help consumers and radio operators resolve
their interference problems. They expect everyone involved to cooperate fully.
Experience has taught them that solutions imposed from the outside are not
usually the best solutions to local problems. Instead, they provide
regulatory supervision of radio operators and manufacturers. To help
consumers, basic information concerning interference solutions is now
available on the Internet through the FCC Consumer & Governmental Affairs Bureau Home Page.
This basic
information includes the CIB Interference Handbook and
the FCC Consumer
Facts Interference Bulletin. Specific information includesthe CGB Telephone
Interference Bulletin,What Can I Do About Interference to My
Radio page and the What Can I Do About Interference
to My Television
page.
The CIB Interference
Handbook includes a list of equipment manufacturers who provide specific
assistance with interference problems. The list also is available through the
Commission's Fax on Demand at (202) 418-2830. Callers should request document
number 6904.
Finally, the consumer has responsibilities, too. You must cooperate with the
manufacturer, the radio operator, and, if necessary, the FCC as they try to
determine the cause of the problem. They need your help to find a solution.
What Causes Interference?
Interference occurs when undesired radio signals or electromagnetic
"noise" sources are picked up by consumer electronics products
-most often telephones, audio equipment, VCRs or TVs. It usually results in
noise, unwanted voices or distorted TV pictures. In most cases, the source is
nearby.
There are three common types of
interference:
(1.) Noise: Interference can be
caused by an electromagnetic noise source. Defective neon signs, bug zappers,
thermostats, electrical appliances, switches or computer systems are just a
few of the possible sources of this type of interference. Both you and your
neighbors may be suffering from its effects. In some cases, the noise may be
the result of a dangerous arc in electrical wiring or equipment and may
provide warning of an unsafe condition that should be immediately located and
corrected.
(2.) Overload: Even if a nearby
radio signal is being transmitted on its assigned frequency, if it is strong
your equipment may be unable to reject it. Your telephone, radio, stereo or
TV should be able to separate the desired signal or sound from a large number
of radio signals and electrical noises. This is shown in Figure 1.
 Figure 1. |
Consumer
electronics equipment manufacturers have worked in cooperation with
government regulators to set and meet voluntary standards of interference
immunity. Modern equipment usually includes enough filtering and shielding to
ensure proper performance under average conditions. Older equipment may not
meet these standards, however, and even modern equipment can be affected if
the interfering signal is particularly strong. In these cases, your equipment
is working as designed, but it may need some additional filtering or
shielding to function properly.
(3.) Spurious emissions: A
nearby radio transmitter could be inadvertently transmitting weak signals on
a frequency not assigned to that transmitter. These signals are called
"spurious emissions." FCC regulations concerning spurious emissions
are very clear. If interference is caused by spurious emissions, the operator
of the transmitter must take whatever steps are necessary to reduce the
spurious emissions as required by FCC regulations. Fortunately, modern transmitting
equipment is manufactured to meet stringent regulations, and many radio
operators are examined and licensed by the government. These federally
licensed operators often have the technical skill to resolve interference
problems that originate from their radio stations.
With all of these possibilities, it is difficult to guess which type of
problem is causing your interference. Usually, only a technical investigation
can pinpoint the cause and suggest a solution. This is where a spirit of
cooperation and trust will pay off! If you believe your equipment is picking
up signals from a nearby radio transmitter, the operator may be able to help
you both find a solution to a mutual problem.
How to Find Help
Most consumers do not have the technical knowledge to resolve an interference
problem. Even so, it's a comfort to know that help is available. Gather
information about interference. The FCC and ARRL have self-help information
packages or books. If the problem involves an electrical-power, telephone or cable-television
system, contact the appropriate utility company. They usually have trained
personnel who can help you and your neighbor pinpoint the cause of the
problem.
Most consumer electronics manufacturers are willing to help you. Your owner's
manual, or a label on your equipment, may give you information about
interference immunity or tell you who to call about interference problems. If
not, the Consumer Electronics Manufacturers Association will be able to give
you the address of your equipment manufacturer's general customer service
personnel. The manufacturers know their equipment better than anyone else and
will usually be able to help you.
Operators of licensed amateur or commercial transmitters usually have some
technical ability. These operators are the nearest source of help. Remember,
the station operator may also be a neighbor! Use a polite approach to ensure
that the relationship stays "neighborly." Licensed Amateur Radio
operators have access to volunteers (Technical Coordinators and local
interference committees) who are skilled at finding solutions for most
interference problems.
Testing One, Two, Three . . .
If you think a neighbor's radio transmitter might be involved, you and your
neighbor should arrange a test. It's important to determine whether the
interference is (or is not) present when the radio station is "on the
air." Your neighbor may want to ask another operator friend to
participate in the test at your home. By the same token, you may want to
invite a friend to attend the test at the radio operator's station. Having
impartial witnesses will make you and your neighbor more comfortable with the
outcome -whatever it may be. Be sure to choose your witness carefully. Select
someone who is diplomatic and tactful.
The tests must be thorough. The transmitter operator must try all normally
used frequencies, antenna directions and power levels. All results must be
carefully written down. More than one set of tests may be needed. Once you
and your neighbor have determined which frequencies and power levels cause
the problem, you'll be one step closer to finding a solution.
Try the Easy Things First
Sometimes, the easiest solutions are the best. Many cases of interference can
be resolved without the need for technical investigations or knowledge. As
first steps, you might check your wiring for damage, for open outer wire
shields, or for loose terminal connections. Try removing any added devices,
such as video games, or even relocating the equipment or re-orienting the
device's antenna and power cord.
If you suspect that the problem is caused by electrical noise, check for
overloaded circuits, frayed wires, loose sockets, etc. These types of
problems should be fixed no matter what! Have your electrician shut off one
breaker at a time, noting if this has any effect on the interference. If so,
determine which devices are connected to that particular line, then remove
the suspect devices one at a time. When the interference goes away, you've
found the "culprit." Your electric utility company service
department will offer assistance if the interference is coming from defective
equipment on the power lines or distribution equipment.
Interference filters for your consumer electronics equipment can be purchased
locally or by mail order. These filters usually eliminate unwanted
interference if they are used properly on the equipment that is in need of
additional filtering.
According to the FCC's Interference Handbook, telephones and other audio
devices that pick up radio signals are improperly acting as radio receivers.
The interference can usually be cured, but the necessary filtering must be
applied to the affected device.
Several companies sell modular telephone interference filters that are very
effective. Your telephone company service department also may be able to
help.
A high-pass filter may reduce interference to an antenna-connected television
or VCR. A common-mode filter should be tried first on TVs or VCRs connected
to a cable system. An AC-line interference filter may help with electrical or
radio interference. These items can be purchased locally or by mail order.
Some interference cures must be applied to the internal circuitry of the
affected equipment. This should always be done by authorized service
personnel.
The ARRL has an information package called "RFI/EMI Radio Frequency Interference". They also
sell a book, Radio Frequency Interference - How to Find It and Fix It, that
provides additional guidance and technical information. Although it was
written for Amateur Radio operators, the book may be helpful to you, too.
Contact ARRL for information about their products and membership services.
Self-Help Cures
In some cases, when all else fails, you may need to resolve the problem
yourself, or with the help of your electronic service person. It's impossible
to use the remaining space to outline all of the possible cures for
interference problems (the subject is quite complex). However, a few simple
cures using commonly available parts can eliminate most problems. The
self-help packages supplied by the ARRL and the FCC explain these cures in
more detail.
Interference Can Be Cured!
Remember, most cases of interference can be cured! It takes cooperation
between the consumer, the manufacturer and the radio operator. With a little
bit of work, you and your neighbor can both enjoy your favorite activities in
peace.
For More Information...
The ARRL and the FCC have self-help
packages available to help you resolve interference problems.
American Radio Relay League, Inc.
RFI Desk
225 Main Street
Newington, CT 06111
Tel 860 594 0214
Internet Web Site: http://www.arrl.org/
E-mail: rfi@arrl.org
Federal Communications Commission
Compliance & Information Bureau
1919 M Street, N.W.
Washington DC 20554
Tel 202 418 0200
Internet Web Site: http://www.fcc.gov/
Consumer Electronics Association
2500 Wilson Boulevard
Arlington, VA 22201-3834
Tel 703 907 7600
Internet Web Site: http://www.ce.org/
For copies of U.S. Government publications,
contact:
U.S. Government Printing Office
North Capitol & H Streets, N.W.
Washington, DC 20401
tel (202) 512-1800
Internet Web Site: http://www.access.gpo.gov/
Sources of interference filter products:
High-pass filters:
Industrial Communication Engineers
RadioShack catalog #15-579, 15-577 (FM Trap)
TCE Labs
Common-mode filters:
Industrial Communication Engineers
TCE Labs
Telephone-interference filters:
Industrial Communication Engineers
K-Com
RadioShack 43-150
TCE Labs
Contact:
Industrial Communication
Engineers
P.O. Box 18495
Indianapolis, IN 46218-0495
tel (800) 423-2666
K-Com
P.O. Box 83
Randolph, OH 44265
tel (216) 325-2110
TCE Labs
2365 Waterfront Park Drive
Canyon Lake, TX 78133
tel (210) 899-4575
Page last modified: 02:42 PM, 16 Oct 2006 ET
Page author: rfi@arrl.org
Copyright © 2006, American Radio Relay League, Inc. All Rights Reserved.
