Power on the Side

When a howling mob of Venezuelans besieged Vice President Richard Nixon in Caracas last spring, the most urgent problem was. to get the word to Washington --fast. But how? Newsmen had tied up just about every telephone line leading out of Caracas; the U.S. embassy's own radiotelephone required a link through a Venezuelan switchboard.

Air Force Colonel Tommy Collins, pilot of Nixon's plane, solved the problem. A dedicated "ham" (amateur radio operator), he had brought along the ham's newest kind of equipment--a portable single sideband transceiver (transmitter-receiver). He nipped open his suitcase, pulled out a breadbox-size radio set, dropped an aerial out the window, in a matter of minutes was talking to ham operators in Washington. The hams called Administration officials on their telephones, hooked their stations into the phone line through a phone-patch, and soon Vice President Nixon's party was talking directly to the White House.

For U.S. hams, such communication has become routine. Since 1957 thousands of them have installed the same 175-watt single sideband (SSB) transceivers in their homes and cars, have become accustomed to chatting with fellow hams in Australia, Alaska or South Africa as they bowl along superhighways on their way to work.

Key & Carrier. SSB makes a transmitter at least four times as potent as an ordinary amplitude modulated (AM) rig of the same power. AM transmitters operate over a wide belt of frequencies--a carrier frequency plus a band of voice frequencies on either side. Radio engineers long ago realized that either of those voice sidebands contained all the necessary frequencies for intelligible conversation. The carrier wave might be likened to the stream of air that is pumped through an organ. By pressing various keys, the air stream is modulated to produce separate notes. In effect, SSB eliminates the basic air stream, sends out only the signals that activate the keys. At the other end, the receiver resupplies the carrier wave, which, combined with the "key" signals, recreates intelligible speech.

Since each sideband uses only one-quarter the power of the original carrier, putting only one sideband on the air saves the transmitter a considerable amount of electrical work. SSB's one narrow sideband takes up less space than AM in the already overcrowded radio frequency spectrum, where the carrier waves of AM stations often beat against each other in whistling confusion. Getting rid of the carrier and one sideband before they reach the transmitting antenna also means that the SSB receiver may be designed for extremely sharp tuning.

Result is that SSB is far more potent than AM, and even as efficient as CW (continuous wave), the old workhorse system of communication that requires all messages to be sent in International Morse Code. A further asset is the ease with which SSB can be "patched" into any telephone line at both transmitting and receiving ends. Thus it enables any householder to telephone, with the help of an SSB operator, almost anywhere on earth.

Patchwork. SSB was used by commercial radiotelephones as far back as 1923. But it showed serious defects when engineers tried to use it for the higher frequencies (3 to 30 me), which cover greater distances by bouncing off the ionosphere. Finally, radio engineers learned how to manufacture the stable oscillators that high-frequency SSB called for. During World War II the Army used SSB between Algiers and Washington, D.C. In 1944 the U.S. Navy established a limited point-to-point SSB circuit between Washington and Pearl Harbor.

But as late as 1954, SSB rigs were considered too bulky and too fragile to serve in the Air Force's far-ranging planes. Goaded on by hams, Collins Radio Co. of Cedar Rapids (no kin to Nixon's Pilot Collins) kept refining and simplifying its equipment, developed a rugged, lightweight mechanical sideband filter that gave SSB sets the needed versatility. Among the most enthusiastic hams were General Curtis LeMay (known as "Curt" to hams all over the world) and his deputy, Lieut. General Francis Griswold (known on the ham air as "Butch")--the two top commanders of the Strategic Air Command. In 1956 Griswold mounted a standard Collins SSB ham rig on his personal plane and took off on an inspection flight to the Far East. No matter where he flew, General Griswold was able to keep in touch with LeMay by talking to U.S. hams and having them arrange a phone-patch with SAC headquarters. Sometimes Butch could talk with Curt directly. The Air Force was convinced.

Just Testing. "We thought of SSB first for what we call our Positive Control System," says General Griswold. This is the "Fail-Safe" system by which planes on an atomic bombing mission can be sent to a prearranged line of departure but may go no farther without specific orders from SAC. "Around the North Pole there is what is called an auroral absorption zone, which gives us trouble in radio communication. And, of course, in our business the North Pole is a very important area. If any radio system can pierce the auroral absorption zone, SSB can. If it can't, we can always use it to relay our signals around the trouble."

The simplicity of relaying SSB signals was demonstrated by SAC's Airborne Electronics chief, Lieut. Colonel Joseph Beler, on a recent polar flight. While headed from Greenland to Alaska over the top of the world, Beler called a SAC base in England by SSB, asked for a telephone connection to headquarters in Omaha, had Omaha patch the call onto SSB again, had it relayed by SSB to North Africa, then relayed by SSB once more to Dhahran on the Persian Gulf. "I could have talked direct to Dhahran," Beler admits, "but I was just testing."

Today almost every SAC plane has its SSB. Service bases all over the world are equipped not only with official SSB equipment, but service-operated SSB ham stations that keep their people in touch with their homes via ham relays and phone-patch. SSB's most emphatic admirers are SAC's high brass, who have seen it turn their telephones into instruments for exercising worldwide command. "Communications is synonymous with command," says SAC's commander, General Thomas S. Power. "If I don't have communications, the only weapon I have is my desk --and I can't throw it very far, and it's not very lethal."

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