It was the early fifties and the threat from the Soviets, our WWII allies, was increasing daily. The
entire military establishment was gearing up for the defense of the North American continent, and
there was serious concern over the ability of the population to survive a nuclear attack by Soviet
bombers.
The belief was that, if the United States were to be attacked, our many commercial broadcasting
stations would serve as valuable navigational aids for enemy aircraft and that those stations
would have to be silenced if an attack came. At the same time, it was recognized that it was vital
to keep the people informed and that the only viable means of disseminating timely information
was via radio.
It was with those considerations that CONELRAD was born, in 1951. An acronym for "Control of
Electromagnetic Radiation," the idea was to deny the Soviets the ability to home in on specific
identifiable broadcast stations, while still providing the American public with an information
medium.
Under the plan, all regular broadcasting would cease when the alarm was given, and all further
broadcasts would be carried out by designated regional stations on the frequencies of 640 and
1240 KHz. (KHz, or kilohertz, was known as Kc. or kilocycles in the US in those days.) It was
hoped that, by concentrating all broadcasting on two frequencies, at lower than usual power, it
would be difficult or impossible for the enemy to single out individual stations for navigation.
All radio and TV broadcast stations, except for the designated CONELRAD stations, were
required to monitor a designated station and to broadcast the CONELRAD announcement in the
event of an alert, then cease transmitting.
It didn't stop with broadcast stations, though. Even Amateur Radio (ham) stations had to monitor
a broadcast station at all times, and to stop transmitting if there was a CONELRAD alert.
Beginning in 1953, all new AM radios sold (FM wasn't that common in those days) were required
to be marked with a "Civil Defense" triangle at 640 and 1240 on the dial.
Times changed and, in the early sixties, an attack by Soviet bombers seemed more remote; the
threat now was from Intercontinental Ballistic Missiles (ICBMs,) which had sophisticated guidance
systems, that didn't rely on radio navigation. Now obsolete, CONELRAD evolved into the
Emergency Broadcast System (EBS,) in 1963.
The EBS was similar to CONELRAD, in that most stations left the air, but the designated EBS
stations continued to broadcast on their own frequencies. At first, the EBS used the old
CONELRAD alerting system, which consisted of the monitored station leaving the air, or
"dropping carrier." This was found to be unreliable and the familiar dual-tone system was
adopted in the 70s. The rules were also relaxed over the years, to permit segments of the EBS
to be used for state and local emergencies.
Due to criticism that it was unreliable, less than responsive to local requirements and because it
relied on a "daisy-chain" of stations, in addition to numerous other technical reasons, the
Emergency Broadcast System began to be replaced, in 1997, by the Emergency Alerting System
(EAS.) This digital system ends, for the first time, the need to rely on intermediate stations, and
can be activated as required by the proper authorities, and the station returned to normal
operations, without the need for intervention by station personnel.
entire military establishment was gearing up for the defense of the North American continent, and
there was serious concern over the ability of the population to survive a nuclear attack by Soviet
bombers.
The belief was that, if the United States were to be attacked, our many commercial broadcasting
stations would serve as valuable navigational aids for enemy aircraft and that those stations
would have to be silenced if an attack came. At the same time, it was recognized that it was vital
to keep the people informed and that the only viable means of disseminating timely information
was via radio.
It was with those considerations that CONELRAD was born, in 1951. An acronym for "Control of
Electromagnetic Radiation," the idea was to deny the Soviets the ability to home in on specific
identifiable broadcast stations, while still providing the American public with an information
medium.
Under the plan, all regular broadcasting would cease when the alarm was given, and all further
broadcasts would be carried out by designated regional stations on the frequencies of 640 and
1240 KHz. (KHz, or kilohertz, was known as Kc. or kilocycles in the US in those days.) It was
hoped that, by concentrating all broadcasting on two frequencies, at lower than usual power, it
would be difficult or impossible for the enemy to single out individual stations for navigation.
All radio and TV broadcast stations, except for the designated CONELRAD stations, were
required to monitor a designated station and to broadcast the CONELRAD announcement in the
event of an alert, then cease transmitting.
It didn't stop with broadcast stations, though. Even Amateur Radio (ham) stations had to monitor
a broadcast station at all times, and to stop transmitting if there was a CONELRAD alert.
Beginning in 1953, all new AM radios sold (FM wasn't that common in those days) were required
to be marked with a "Civil Defense" triangle at 640 and 1240 on the dial.
Times changed and, in the early sixties, an attack by Soviet bombers seemed more remote; the
threat now was from Intercontinental Ballistic Missiles (ICBMs,) which had sophisticated guidance
systems, that didn't rely on radio navigation. Now obsolete, CONELRAD evolved into the
Emergency Broadcast System (EBS,) in 1963.
The EBS was similar to CONELRAD, in that most stations left the air, but the designated EBS
stations continued to broadcast on their own frequencies. At first, the EBS used the old
CONELRAD alerting system, which consisted of the monitored station leaving the air, or
"dropping carrier." This was found to be unreliable and the familiar dual-tone system was
adopted in the 70s. The rules were also relaxed over the years, to permit segments of the EBS
to be used for state and local emergencies.
Due to criticism that it was unreliable, less than responsive to local requirements and because it
relied on a "daisy-chain" of stations, in addition to numerous other technical reasons, the
Emergency Broadcast System began to be replaced, in 1997, by the Emergency Alerting System
(EAS.) This digital system ends, for the first time, the need to rely on intermediate stations, and
can be activated as required by the proper authorities, and the station returned to normal
operations, without the need for intervention by station personnel.
CONELRAD (Control of Electromagnetic Radiation) |
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