RCA Computer

The RCA FC-4101 computer was the ‘heart and brain’ of the FPQ-6 radar. In 1964 and for some time after, the FPQ-6 was the only operational radar with a self-contained general purpose computer.

All known mechanical and dynamic tracking inaccuracies were programmed into the computer to provide immediate correction of range and angle outputs, compensating for such errors as out-of-level azimuth-plane and elevation-gear irregularities, dynamic lag, and reflector droop effects on null shift and beam squint. It could also predict the continued path and range of the target so that if the target was lost in low signal-to-noise conditions the antenna would move ahead under its control to perhaps reacquire the target. And to make it easier for human operators it displayed all tracking data on decimal displays. The 4101 was quite a sophisticated machine with only four module types utilizing NOR logic for all its functions. The modules were built to BMEWS (Ballistic Missile Early Warning System) standards using stainless steel metalwork – built to last.

It was surprising how much was accomplished using the RCA FC-4101 computer’s 4K memory - upgraded later to 8K, and then finally to 16K in 1970; still only a little more memory than the first office and domestic personal computers appearing seven or so years later. [1