In 1955 Collins Radio had developed the necessary ingredients to bring about a revolutionary change in the field of high frequency single sideband communications. Those key ingredients were the Collins Mechanical Filter for excellent selectivity, the Permeably Tuned Oscillator (PTO) for linear tuning accuracy and high frequency stability, and RF feedback techniques for highly linear power amplifiers. The first HF SSB products out of the Collins factory were the 75A-4 Receiver and the KWS-1 1kW Transmitter. They were introduced in March 1955 and advertised for the amateur radio market. But the price was so high that few hams could afford them and soon the community labeled the equipment as “The Gold Dust Twins” because they perceived it took a bag of gold dust to buy them. Collins Radio even offered to sell the equipment with monthly installment payments.

At that time Collins Radio was well staffed with technicians, engineers, administrators, and managers who were licensed amateur radio operators. After all, Arthur Collins, the company’s founder and President, was also a longtime ham – W0CXX. So it’s very probable that introducing Collins HF SSB into the amateur product line was a carefully calculated marketing strategy to gain maximum exposure with minimum company resource expenditure.

Over the next few months Collins sent a couple of 75A-4 receivers and KWS-1 transmitters to Gen. Curtis LeMay, Commander-in-Chief of the USAF Strategic Air Command (SAC) and Maj. Gen. Francis Griswold, Vice-Commander-in-Chief of SAC. Both were amateur radio enthusiasts holding call signs K0GRL and K0DWC respectively. They were friends of Arthur’s and well acquainted with Collins equipment. The new equipment was installed in the Military Affiliate Radio System (MARS) station on Offutt AFB in Nebraska. Arthur Collins personally checked out the equipment on-the-air operation with Generals LeMay and Griswold. This new equipment introduced a new modulation mode called single sideband (SSB) which offered many advantages over the existing amplitude modulation (AM) mode currently in use.

An AM transmitted signal consists of a carrier and two identical sidebands that each carry the information. The transmitter available peak output power is divided with half going to the two sidebands and the remaining half going into the carrier (which contains no information). Single sideband modulation eliminates the carrier and one of the two identical AM sidebands. Thus all of the available transmitter power is devoted to the remaining single sideband. The information is therefore transmitted with 8 times more power using SSB rather than AM for a given transmitter peak output power capability. The revolutionary and highly compact Collins Mechanical Filter allowed only the single sideband to pass through the circuitry and replaced an entire rack of equipment then in use for SSB modulation.

On the receiving end the SSB signal has another 2 to 1 advantage over AM because the occupied bandwidth is only half as wide as AM and therefore only half as much ambient noise on the received information signal.

By March 1956 Collins technicians and engineers were installing the “Gold Dust Twins” aboard a Strategic Air Command (SAC) C-97 transport airplane at the Cedar Rapids Airport. The plane would then begin a series of long flights to evaluate the feasibility of using HF SSB for command and control of the nation’s strategic bomber defenses. This was during the Cold War and it all came about via the friendship and vision of three amateur radio enthusiasts – Arthur Collins, W0CXX; Gen. Curtis LeMay, K0GRL; and Maj. Gen. “Butch” Griswold, K0DWC.

It is a remarkable technology adventure story – especially considering the “radio operators” aboard the C-97 were Arthur Collins and “Butch” Griswold. Here are the details of these flights, compiled from various sources, followed by a summary of the Collins HF SSB legacy with the USAF that was spawned by these early demonstration flights.

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