April 1959 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Whoa! 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 noise.
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.
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 tuning dial.
"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
Sadly, the operator turns off the receiver, and the family
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
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 speaking!
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
Jamming Techniques. 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
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.
Ground-Wave Jamming. 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 transmitter completely.
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!
Sky-Wave Jamming. 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 jamming signals.
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 signal.
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.
The usual 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 watts!
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
Careful 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