Art Collins used Project Bird Call to demonstrate the superior performance of single sideband in 1956. This experiment changed long distance HF communications forever. 

Major leaps forward need champions. For single sideband, these were two U.S. Air Force Generals – Curtis LeMay and Francis Griswald on the customer side – and Art Collins on the vendor side. All three were active hams. General LeMay commanded the Strategic Air Command. He was looking for ways to improve HF communications with his B-52 Bombers. Butch Griswald was Lemay’s number two. Art ran Collins Radio, a major supplier of military communications and avionics. Previously, Collins had invented the mechanical bandpass filter and permeability tuned oscillator. It turns out that these developments made SSB radio transmission practical for the first time.

Reliable long distance HF radio was critical to Strategic Air Command in the 1950’s. In particular, LeMay wanted to be sure that he could recall his bombers if necessary if their mission was to be safely aborted. So the three designed an experiment. Collins ham SSB gear was installed in a C-97 aircraft. This B-29 bomber, converted for passenger use, then made two very long distance flights from the U.S. One flight to Asia, the other to Greenland. All along the way, they tested SSB with amateurs and military bases. Their goal was to make sure they could communicate with SAC headquarters at Offutt Air Base in Omaha.

General LeMay called the flights Project Bird Call.

Project Bird Call – A Success for Single Sideband

LeMay’s experiment was a big success. Project Bird Call clearly demonstrated the superiority of SSB over AM for long distance HF communications.

Collins installed off the shelf amateur radio gear for these tests, as shown above. The receivers were the venerable 75A4 receiver, and KWS-1 600 watt sideband transmitter. These flights comprised over 120 hours of flight time and made nearly 2,500 long distance radio contacts in the spring and summer of 1956.

By 1957, both the U.S. Air Force and Navy began switching to SSB for long distance HF communications. Collins Radio was the prime supplier of more than 80,000 installations over the next 30 years.

The Collins gear used in Project Bird Call was proven on the ham bands in prior years. The 75A4 receiver was first manufactured in 1955. It was an enhancement of the existing 75A1-3 series that featured a mechanical filter. The KWS-1 was the matching transmitter. Together they were called the gold dust twins.