Amateur radio operators have been
blamed for a lot of radio frequency interference (RFI) and television interference
(TVI) over the years, with some being justified and a lot being unjustified. The
surest sign that a Ham set is interfering with your entertainment box is when you
actually hear voice or a series of dits and dahs. However, when the interference is a
steady or waver buzzing sound or scratchy intermittent hash, chances are greater that
the interference is coming from a noisy motor in a vacuum cleaner, a kitchen blender,
a power tool, or an arcing power line transformer / cracked insulator. The American
Radio Relay League (ARRL) has jumped through burning hoops (figuratively) to educate
licensed operators on how to avoid complaints by assuring gear is functioning
properly, and educating the public about the likelihood that the problems they
experience are not coming from the guy down the street with big antennas in the yard
but from the next-door neighbor's swimming pool filter pump.
TVI and the "Dallas Plan"
By the Editor
One of the important subjects discussed at a recent meeting of the Radio-Television
Manufacturers Association (RTMA) was the problem of amateur radio interference to television service.
Such interference has been of major importance in many metropolitan areas, where crowded
living conditions have placed hundreds of television receivers in close proximity to
amateur stations. In some cases it has served to force the amateur off the air during
television hours because of public wrath and indignation due to a misunderstanding of
all the facts.
The desire of the public in fringe areas for television reception has also aggravated
the interference problem. When receivers are used in areas of low signal strength, even
the slightest interference from amateurs or other services becomes a major problem.
The Amateur Radio Activity Section, under the chairmanship of Al Kahn of Electro-Voice,
discussed the correlation of the service managers' efforts and amateur activities. Both
the RTMA and the FCC have set up standards for receiver performance dealing with radiation,
It should be realized that the service industry has done a tremendous job overnight
in acquainting service technicians with the many problems of the complex television industry.
From a total of 10,000 receivers in 1945 to the present total of over 15,000,000 sets,
it has been a tremendous job to train sufficient technical help to handle the servicing
of these receivers with their many attendant problems.
In spite of the many excellent service manuals published by manufacturers, and the
articles in various publications dealing with the problem of amateur interference, there
has been little done to directly acquaint the technician with amateur interference and
the remedies. Too often the technician is inclined to blame any type of interference
on the neighboring amateur, especially if the amateur antenna is clearly visible. Some
of this blame is due to misinformation or to inadequate training. In the majority of
cases there has been no concerted effort on the part of technicians to work with the
offending amateur to conduct tests designed to eliminate or reduce this interference
to a negligible value.
Too often the ham has been blamed for interference from neon signs, electric razors,
and other assorted interferences. Part of this is due to lack of education in recognizing
amateur interference, or confusing it with other types of interference.
A television receiver offers its own built-in analysis method for most troubles, and
the problem boils down to interpreting what you see on the screen.
Too often, the general public regards the amateur as a person who pursues a hobby
to the detriment of their entertainment. The many valuable services rendered by the amateur
usually go unnoticed. Amateur radio is a vital part of the communications system of this
country and has the full backing of government and military authorities. No other service
can offer adequate emergency facilities, as attested by the sterling performance of amateurs
in time of floods, hurricanes, and other disasters.
The Federal Civilian Defense Administration has recognized the amateur service's value
and has made provisions for stations in this service to be operated in the event of national
emergency. According to the FCDA, vital services such as these are not to be disrupted
during time of emergency.
If the problem of amateur interference grows worse, a great many amateurs will either
give up their hobby in sheer desperation or reduce their operating time to such an extent
that their value will be considerably lessened.
The logical solution to this problem is cooperation between the amateurs and the service
groups. Almost any town of appreciable size has a service organization as well as amateur
clubs. If the amateurs will contact these service organizations, and arrange to have
one of their technically qualified members attend service meetings, techniques for eliminating
the interference can be readily worked out. Essentially this is the method commonly known
as the "Dallas Plan," and this plan has been eminently successful wherever tried. If
this or some similar plan were widely used, the problem could soon be solved.
To further increase the supply of adequately trained technicians, the RTMA has recently
taken steps to make good technical training available.
RCA Institutes is currently preparing a three-year syllabus for use in vocational
high schools. This syllabus is designed to acquaint high school students with the vocational
possibilities of television and will contain material on amateur radio.
The RTMA is very cognizant of the interference problem and is willing to furnish manufacturers
with many suggestions for improvement of receiver performance. It is very helpful to
the service technician if the manufacturer's service manual contains information on the
types of amateur interference and methods of recognizing them, as well as suggested cures.
There is also a movement among manufacturers to include a built-in, high-pass filter
in the receiver. In many cases, a high-pass filter has not eliminated interference due
to improper installation, and this can be effectively controlled if the filter is installed
at the time of manufacture.
Onowa, Iowa recently passed an ordinance making it illegal to operate an amateur transmitter,
diathermy machine, or any other device causing interference to television or radio regardless
of where the fault lies. Such an ordinance is obviously invalid, but it will require
a concerted effort plus a great deal of expense to make a test case of this or similar
ordinance and prove its invalidity. While this ordinance, in itself, is not too important,
it does indicate the type of opposition faced by amateur radio, due to misinformation.
Posted January 15, 2019