April 1959 Popular Electronics
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.
Take a look at the RF feedthrough and lightning arresting choke on the
feed line on the original Voice of America transmitter in Munich, Germany.
Now that is serious stuff. This story from an early Popular Electronics
reports on the extreme lengths to which the Soviet bloc went in order
to prevent its countrymen from hearing radio signals broadcast by the
Voice of America and other non-state-approved beacons. Quarter megawatt
transmitters sent messages of freedom that could be picked up by even
the most remote crystal sets that didn't have the advantage of amplification.
Ground-wave, sky-wave, and short-wave jamming techniques were employed
to ensure the only signal that could be received was a buzz-saw type
Not so long ago, and certainly in 1959, America was viewed
as a beacon of freedom, both figuratively via word-of-mouth and underground
newspapers, and literally via high powered radio broadcasts directed
into cordoned off countries ruled by Communist rulers. Herculean efforts
were made by the likes of Stalin, Khrushchev, Castro, Kim Il-sung, Pol
Pot, and various other despots to prevent any form of communications
with the outside world. I remember back when my grade school classmates
and I were practicing hiding under our desks in the event of a nuclear
bomb attack, how the teacher would tell of something as benign (to us)
as a Sears, Roebuck catalog not being permitted beyond the Iron Curtain
lest the people learn about what they are being denied by their dear
leaders. Denim blue jeans and automatic washing machines were deemed
to be the spawn of evil Capitalism. Such devices were according to the
Communist propagandists prima facie evidence of how a free, industrious
people thrived while the slothful (never identified as such) were mired
in misery. Why should some people be happy and some not, when everyone
can share in being miserable together? A 'worker's paradise' was the
promise of every tyrannical regime. Multitudes of mass graves the world
over show how well that always worked out. To this day we suffer the
whims of powerful men and women who believe that the only reason Communism
has failed is because the right people haven't tried it yet.
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By Will Bohr
It is nearly 0400 hours, Moscow time. In a corner
of the Soviet capital everyone sleeps except for one family which is
huddled over an ancient short-wave receiver. The operator adjusts the
"Just one minute more," think the early morning
listeners. The radio signal the Russians are listening to comes in loud
and steady, with a slow rolling fade which indicates that there are
thousands of miles separating these listeners from the transmitter about
to speak. Everyone catches his breath as the voice from the loudspeaker
comes to life:
"This program is coming to you from the United
States of America. The following news program is brought to you in the
Russian language ..." Suddenly the room is filled with a gathering roar
that blots out the voice they are so eager to hear. The noise whipsaws
across the signal and burns in their ears. Frantically the operator
turns the dials of the receiver, trying to escape the unintelligible
chaos of noise smothering the voice of the free world.
the operator turns off the receiver, and the family disperses...
The Soviet Union started deliberate radio interference with
the Russian language broadcasts of the United States and England shortly
after the end of World War II. At the present time over 2500 separate
jamming stations are scattered throughout the USSR and the satellites
in an effort to blanket reception of the 85 transmitters of the Voice
of America. They try to blot out all 16 frequencies used by the VOA.
When the Polish government ceased its radio jamming operations a
few years ago, it informed the world of the cost of these operations.
For every dollar spent by the Voice of America to produce the Polish
language programs, the Polish government spent over one hundred dollars
in a vain attempt to obliterate reception!
Three separate jamming transmitters must be employed to "protect"
three cities from one Voice of America transmitter, as shown
above. A single high-power jammer at point "X" wastes power
over unpopulated areas. Separate jammers provide maximum suppression
in the cities, but leave countryside free from interference.
The total cost of the Communist jamming effort is estimated at over
100 million dollars. The evident fear of Voice of America operations
is shown by the fact that the Soviets jammed the United Nations broadcasts
over the VOA, even during the periods when the Soviet delegates were
Jamming a high-power
radio station is a complicated as well as an expensive job. The general
jamming technique takes the form of superimposing random noises and
sounds upon the identical carrier frequency of the offending transmitter.
Since it is usually impossible to locate the jamming equipment near
the station to be jammed, the "jammer" is generally placed close to
large population centers, where there are conceivably many receivers
capable of tuning to the channel of the politically undesirable station.
The jamming signal usually consists of a buzz-saw-like noise, or
random musical tones superimposed upon a steady buzz, much in the manner
of a bagpipe. In rare instances, the jamming transmitter superimposes
a program of its own atop the unwanted station. Jamming stations generally
identify themselves by a two-character call sign, which may change frequently.
Radio communication during
daylight hours in the broadcast band (500-1600 kc.) normally takes place
by means of the ground wave, that portion of the radio wave which travels
along or over the surface of the earth. Its usable range is a hundred
miles or so.
Short-wave signals are reflected back to earth
by the ionosphere so that cities "A" and "D" (in diagram above) must
each have a jammer. A shift of frequency of the transmitter or a change
in the ionosphere can project the signal to cities "B" and "C." so that
all four cities must have separate jamming equipment to suppress a single
The power of many European
broadcast stations is about 150,000 to 250,000 watts (compared to a
maximum limit of 50,000 watts in the United States). These stations
are capable of producing a strong signal on even the most primitive
radio receiver. To obliterate this signal over a small area such as
a single city, a jamming transmitter of 10,000 to 15,000 watts may be
employed. However, when it is desired to jam a large area of several
thousand square miles, it is either necessary to use many jamming transmitters
of this power spread over the area, or else one or two high-powered
jammers equal to or greater in strength than the undesired station.
In general, the former technique seems to be in use, at the present
time as twenty or thirty jammers are usually employed to block out the
broadcast-band transmissions of the various VOA transmitters in Europe.
The Soviets have found to their sorrow that a jammer signal weaker in
strength than the undesired signal is worse than useless; it merely
calls attention to the station that is condemned for obliteration!
During the evening hours, the
characteristics of the broadcast band change, permitting excellent reception
from stations many hundreds of miles away. This permits the VOA to reach
deep within the Soviet Union with its programs of news and information.
Antenna tower base of the million-watt Voice of America transmitter
in Munich, Germany, showing the feedthrough insulator and lightning
surge loop. The high-power broadcast station can override most
Since the jamming equipment is not near the transmitting station, the
jamming signal does not "overlap" the broadcast reception of the offensive
station at points within Russia. This forces the Soviets to employ additional
jamming equipment at various places. Dozens of jammers may be required
to silence effectively a single radio station in a few populated areas,
leaving relatively good reception of the unwanted station in sparsely
settled areas.Short-Wave Jamming.
Due to the
nature of short-wave propagation, a powerful short-wave transmitter
is capable of blanketing tremendous areas of the Soviet Union, all of
which must be covered by competing jammers in order to obliterate the
signal. The action of short-wave "skip" is a result of the transmitted
wave being radiated up into the ionosphere to be bent downward in a
reflected ray returning to earth a considerable distance from the transmitter.
The amount of bending and distance covered depends upon many factors,
most of which are uncontrollable. Separate jamming stations must be
employed at each "skip point," since the "skip distance" of the jamming
signal cannot be relied upon to be the same as that of the offending
It can thus be seen that the problem of silencing literally
hundreds of stations operating on various broadcast and shortwave frequencies
is an extremely large operation.Equipment Used.
Special transmitting stations for jamming operations have been developed
by Soviet engineers. These stations are designed for rapid frequency
shifting and are capable of heavy noise modulation.
modulation consists of a buzz-saw noise that completely fills a band
of five or six kilocycles each side of the carrier frequency. Jamming
equipment of this type is known to have power levels up to 1,000,000
As auxiliary jamming equipment, the Soviets sometimes
press broadcasting stations into use, transmitting noise and chaos instead
of the usual programs.Anti-Jamming Techniques.
Well aware of the jamming operations, the VOA and the British Broadcasting
Corporation have several techniques at their disposal to combat jamming.
The most obvious and effective technique is to increase the power
and range of the existing stations, and to add more stations, thus improving
the coverage of the USSR. The VOA, for example, now broadcasts about
500 "transmitter-hours" (hours of broadcast multiplied by number of
transmitters) daily to the Soviet Union, the satellites, and Red China.
A second technique is to change the wavelength (frequency) of the
transmitting station, thus evading the jammer. This is usually impractical,
as the Russians monitor the station being jammed and are quick to retune
the jamming equipment when any frequency change is noted. Also, abrupt
frequency changes make reception difficult for the listener.
Another evasive action is to choose a transmitter frequency immediately
adjacent to the frequency used by a Soviet broadcast station, so that
the program cannot be jammed without jamming the Russian broadcast.
Is Jamming Effective?
Proof that the VOA programs
are penetrating the barrage of jamming is evident from the amount of
abuse heaped upon this activity by the Soviet Government.
screening of refugees pouring into Berlin from the east confirms the
value of every dollar spent in the electronic war. Clandestine listening
posts behind. the Iron Curtain listen to the voices of freedom and report
reception. Also letters smuggled out of the Soviet zones of influence
attest to the impact these broadcasts have upon their audience.
It is therefore well known that the broadcasts do pierce the interference,
and are successful in combating the efforts to prevent the flow of information
and truth from reaching the citizens of the Soviet Union.
Posted October 29, 2013