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 a 1959 issue of 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 free world.
Sadly, 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.
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.
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.
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!
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 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.
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.
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.
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 Government.
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 January 2, 2023
(updated from original
post on 10/29/2013)