Do you remember the pair of tiny triangles that appeared on the tuning dial of your transistor radio in the 1960's?

What were those for?

In the early Cold War era, our government believed the predominant threat to America was from the Soviet Union. Soviet bomber aircraft would have been the primary vehicle for carrying atomic weapons to our shores. These bomber aircraft would have flown across the icy wastes of the North Pole.

The D.E.W. (Distant Early Warning) line was a radar picket constructed across northern Canada and Greenland, with the intent of watching for such a sneak attack.

Signaled by operators on the D.E.W. line, American interceptor jets, always on alert, would have hurtled skyward to turn away the attacking waves.

But some enemy bombers would surely have survived, and pressed on toward their targets. (In Michigan, that would have meant K.I.Sawyer AFB and Kinchloe AFB in the U.P., the Soo Locks, our major cities, and many other locations...)

Our military reasoned that in the last leg of their flight, Soviet bombers could find their targets by homing in on radio signals from AM radio broadcast transmitters here in the United States.

The idea certainly could have worked. (Actually, not too many years ago, private pilots often navigated in the same manner. In the pre-GPS era, all aeronautical charts included a list of AM radio stations with their frequencies and exact locations, for that legitimate purpose.)

So a system to control radio station broadcasting was developed. It was known as CONELRAD, for Control of Electromagnetic Radiation.

How did the tiny triangles on the radio dial fit in?

The Federal Government mandated that in event of an attack, the CONELRAD system would be activated. This meant that non-essential radio stations would stop transmitting. To keep vital information flowing to the public, though, some regional stations would continue broadcasting, but they would move to one of only 2 frequencies - those frequencies marked by a triangle on the radio dial.

The hope was that this would confuse and deter enemy bombers, by throwing them off course. The radio station they thought would be on a certain frequency and guiding them to their target, wasn't, and the stations still broadcasting were all crowded on just a pair of channels.

They would have flown over the pole, expecting to hear Elvis, or the Top 40 being played, but instead would have heard a jumbled cacaphony of warning messages packed on just 2 channels, with the rest of the AM band dead silent...