August 1945 Radio-Craft
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
Hugo Gernsback, as I have
often pointed out, had a penchant for predicting technology development and user
trends. Decades of researching and publishing articles and books, inventing
electrical and mechanical devices, and creating educational material enabled a
synergistic combination of real-world experience and visionary thinking. In this
1945 Radio-Craft magazine editorial entitled, "The Radio Alarm,"
Mr. Gernsback envisioned a form of public emergency broadcast system that would
notify the public of impending and/or in-process dangers like natural and
man-caused disasters, invading armed forces, police alerts, etc. His idea
involved incorporating a special always-on circuit into radios that would listen
for a broadcast tone and then switch the radio on automatically. Of course in
1945 there would need to be a minute of two allotted for the tubes to warm up
before sending out the actual message. In 1951 the
CONELRAD system was put
into operation to alert citizens in the even of a Cold War era invasion or
attack, doing exactly what Gernsback had envisioned, albeit without a the
special turn-on circuit. Then, in 1963 the more familiar
Broadcast System (EBS) took over. Finally (for now), the
System (AES) replaced the EBS. Automatic turn-on never was implemented;
however, given that most people are permanently attached to their cellphones,
which are always on, there is really no longer much need for it. People like me
who almost never have a cellphone turned on, will likely miss the opportunity to
get into the fallout shelter before the radioactive wavefront passes through
- unless an alert comes over the wireless set.
Editorial: The Radio Alarm
... Postwar radio developments urgently require a device which will make
it possible to notify owners of radio sets by means of visual or aural signals
Owners of radio sets for some years past, have felt the urgent need for a
device which would automatically turn on their receiver when important news
The death of President Roosevelt demonstrated the potential importance of
such a device. Many people did not know of the President's death until hours
after the news had been broadcast. In time of impending disastrous floods, earthquakes,
tornadoes, great fires, sudden war (such as Pearl Harbor), our radio sets should
be equipped with a simple and sure device whereby it will be possible for a
broadcast station to turn them on if such an emergency should arise.
During the next few years we will have handie-talkies and other portable
radios coming into use. These will not function unless they are equipped with
a positive radio alarm. The person afield must have a means of knowing that
he is wanted and should listen in. It is obvious that he cannot listen in continuously.
For war purposes there is not such a great necessity for a radio alarm. When
a soldier carrying a walkie-talkie, or handie-talkie, wants to talk to headquarters
or to a command post, someone there listens in at all times. Obviously this
is impossible for handle-talkies as well as walkie-talkies under peace conditions.
Here then we require either a visual signal such as a flashing lamp, a red
or other colored disk that would suddenly appear, or a bell or buzzer. In our
home radio sets the problem is not so very difficult, it merely requires a special
radio pilot tube which is turned on continuously. Then when the alarm signal
comes in the signal will trip the relay and the set is automatically turned
The modus-operandi at the broadcast station will be that a special tone or
musical note of a specified characteristic is emitted. Such a special signal
will be broadcast only during an emergency where it is of utmost urgency that
all radio listeners shall be informed of the news about to be heard. There are
no technical difficulties in all this and we have the means to do it today.
There only remains the economic problem that the special pilot tube must be
kept turned on-24 hours a day. That means a certain amount of current will be
used right along and further that the life of such tubes - constantly operating
for months and years - will be comparatively short. It also follows that such
tubes or devices must be replaced periodically. The cost of replacing them would
not be a great burden. Most listeners will be willing to pay for it, because
it will be their insurance that if news of national or international importance
occurs, they will be informed instantly.
When it comes to portables such as walkie-talkies, handie-talkies and others
the problem becomes more complicated because these use batteries. If the batteries
have to be kept in the circuit continuously they will soon wear out. Here then,
we require a different type of radio alarm, which should draw very little or
no electric current from the batteries. This problem is not insoluble either.
We can, for instance, with good results resurrect the old-time coherer, which
was superseded by the radio tube and became obsolete at that time. The coherer
is a simple device which uses almost no current at all, except when electromagnetic
waves strike it and make it operative. The regulation coherer is not a sure
device but the Marconi vacuum-exhausted cohereris pretty rugged, even against
shocks. Moreover, even in Marconi's days it was possible to eliminate extraneous
waves; such for instance as those created by lightning and other stray charges.
A number of patents on such weeding-out circuits were taken out by the Marconi
people almost a generation ago. It should be possible to further perfect the
vacuum coherer and make it completely reliable under all circumstances. This
does away with using an electronic tube. Practically no battery current is used
- until the special signal energizes it, which trips a simple relay and puts
the receiver into operation.
It is quite possible that the coherer idea will be brought up to date in
such a way that it can be used universally and with the efficiency of a modern
The coherer, furthermore, has a certain advantage in that it can be manufactured
much cheaper than a radio tube. A simplified relay can also be manufactured
at a very low cost today. It will be seen that by this combination of an old-time
device, radio may get an efficient alarm that works under all circumstances.
There may be many other ideas as to how the problem can be solved in an equally
efficacious manner, by other radio-electronic means which may work even better
than the coherer.
One thing is certain, the radio alarm is a device which is badly needed.
Our radio technicians and experimenters will find this a fascinating and promising
field in which to do further research and developing work.
If readers have any worthwhile thoughts on the above, Radio-Craft will be
happy to receive suggestions and ideas on the subject.
Posted February 8, 2021