The control system of the PCP90.

 

This camera and it's radio based digital control systems was a significant development in the history of television cameras. It led on to the Philips/Norelco PC-100 Triax camera from which the very successful Philips LDK5 camera is descended from. The principles of the data control systems and sending the complete coded picture, on various subcarriers, in these cameras led to similar control systems on most of the worlds Triax cabled cameras.

 

References:-

"This is Colour" International Broadcasting, undated supplement.

"Television Broadcasting Camera Chains", Harold E. Ennes, pub 1971, page 81.

"A Digitally Controlled Miniature Colour Camera" British Kinematography Sound & TV, Feb. 1971 p44-51.

Dave Le Breton writes:-

I know quite a lot about the BBC PCP90 Minicams as I was involved in the project from the beginning and took it over when my then boss left in 1971.  The BBC bought two PCP90s, together with the radio kit (microwave vision and 141MHz command data) and two purpose-built vehicles.  These were a cross between an SCU and a radio links van and were my first attempt at doing a vehicle.  The vehicles were meant to carry enough kit to enable the Minicam to operate independently, but the most important facility was to provide a dry warm environment to align/mend the beast.

The PCP90 had the same design philosophy as the LDK5 - everything to produce PAL at the camera end, with a data signal to provide operational control and genlock.  It was therefore very flexible and pioneered helicopter operations etc.  This approach to camera design was absolutely contrary to the official BBC Engineering thinking at the time which aimed to minimise the amount of processing at the camera end, but OBs saw the potential and realized it.  Its first on air use (as a radio camera) was during field trials at the Open Golf & Commonwealth Games in 1970.

Our cameras were purchased through Pye TVT, who reworked the cameras for 625 PAL.  I did hear that a third PAL version was produced for a European customer, but can't confirm this.  They were actually updated to PCP90B standard before being put into service - giving the luxury of plug-in boards in the camera head (they were hard wired).  We did have the full base station kit and by today's standards it was very big.

The use of Lemo connectors for BBC triax dates back to the choice made for the Minicams.  The data stream had slots for control of six cameras as standard, but we modified ours for a maximum of two, but with three times the update rate.

As to the origins of the Minicam, I seem to remember hearing that it was originally hoped to use an all-electrostatic tube that never came to fruition.  Whether this was before or after Philips (Norelco) took it over, I don't know.  The cameras that we had used bog-standard XQ1070 series 25mm plumbicons. The picture quality often left something to be desired, but the control system was clever for its day - no microprocessors then!  The variable control settings were stored in the backpack in analogue memory - a high quality capacitor across a fet, with a relay to feed in current pulses of the appropriate polarity.  It sounds primitive, but it worked.