Designs Department - Reminiscences |
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| Some incidents at Western House By Peter Tingey TELSTAR 1 It must have been a day in 1963 or 1964 when Gordon Parker showed a couple of visitors into the laboratory. They were carrying electronic equipment which they placed on a cleared bench. A separate mains supply was arranged and the equipment was powered and left to warm up. Later Gordon and one American engineer returned and they inspected the equipment output signal. A remark was made that it was still warming up and Gordon mentioned that the 525 line N.T.S.C. colour signal was available at the laboratory's racks and he showed the signal on an oscilloscope, vectorscope and colour monitor. The American was impressed and he said that they could use this signal, he also noted that all the rack equipment was transistorized. He switched his equipment off as Gordon plugged the local signal to line. This was available at Goonhilly Downs for the Satellite tests. Maybe this was the first Colour Signal to pass via a satellite from the U.K. to the U.S.A. Panic in Western House? Never! In July 1963 Designs Department had carried out many tests on the colour television systems then available and a demonstration was arranged for the European Broadcasting Union to be held at Western House and Broadcasting House. This required every colour monitor, encoder, decoder and test apparatus to be in use on the day. The extent of the preparations can be gauged from the mass of cables that hung across Hallam Street from Western House to Broadcasting House. About ten minutes before the delegates were due to arrive I was at Peter Rainger's recording display area on the ground floor when he remarked that his monitor display was soft and lacked focus. A quick check showed that the tube was inferior. But there were no spare monitors. I phoned to section 8 laboratory and spoke to Gordon Parker explaining the problem and asking him to send down a new boxed tube 21CYP22A. Returning to the monitor, I disconnected it and with help placed it on its face on the carpet - as Peter Rainger quietly left the room. I removed the dud tube and was ready when the new tube arrived. The reciprocal proceedure restored the accessories to the new tube and the monitor was soon on its dais. After satisfactory alignment and adjustment with test signals all was correct as Peter Rainger returned to his demonstration with minutes to spare. This was the best monitor display of all. I had heard that RCA productiuon allowed 4 minutes to change a colour tube. Metric or Imperial? In 1964 a group of Russian engineers visited Designs Department and were shown the Colour Television systems that we were working on at the time. In conversation they admitted that they were rather impressed with our shops in Oxford Street. An engineer remarked that he had purchased some cigarettes and was amazed that the 'women' cashier could state the price and immediately work out the correct change in shillings and pence. Which even he found difficult. In December , when in Moscow, I remembered this comment and I went to the hotel postal service counter and asked for thirteen x eight copeck stamps. The assistant, 'a women' set up the abacus and tried to multiply eight by thirteen. She asked a colleague for assistance and the two tried without success. They turned to a mechanical calculator and set in eight and operated the adding handle thirteen times to get to the sum 104 I had been waiting for. The advantage of Imperial is proved.
280,000 Holes in a Shadow Mask
The telephone switchboard at Broadcasting House often had technical enquiries and the operators had found Designs Department personnel capable of responding to these callers. I happened to answer the laboratory phone one day and the caller was a sales person at a large Midland Metal Work factory. He wanted to know whom to contact with regard to quoting for the machining of the Shadow Masks used in the new colour tubes. I asked what operation he was interested in and he suggested the drilling operation. I pointed out that a 21 inch diameter mask had more than 280.000 holes. He replied that they had got a multiple head drilling tool. I continued " and each hole is countersunk". The response was a quiet "Oh" and I explained that an etching process was used in the manufacture and it was similar to the etching of printed circuit boards. The call now ended--- but I was left with the impression of a poor chap applying a drill to a shadow mask as he said 200,001 200,002 200,004 200,00---dam, start again!
Microwave Link
It is quite usual for a project to require days or months of development work in the laboratory before the required results are achieved. But sometimes there is a flash of inspiration and solutions are almost immediate. One Friday Gordon Parker asked me if I could find time to look at a microwave link (Transmit and Receive) assembled at the end of the laboratory. The monochrome signal performance was satisfactory but the colour signals experienced about 20 degrees differential phase and extensive differential gain. This was characteristic of all such link equipment. I was rather busy at the time, but I suggested that I would have a look at it on Saturday morning. Being the only one in the laboratory on the Saturday meant that I could concentrate on the problem without distraction and my first measurement confirmed the distortion of the colour test signal. Looking at the signal passing to the Klystron modulator all seemed correct, indicating that the Klystron stage could be the problem. Inspection showed that the supply terminals on the Klystron, not conveying the video signal, were not decoupled. Applying suitable capacitors from these terminals to chassis took only minutes and the measured distortion of the colour signal was now negligible at 0.1% differential phase and slight differential gain. I attached a note to the drawings stating the component additions and new performance. On Monday I told Gordon of the improved performance of the link equipment and it was soon removed from the laboratory. I later heard that the change information had been despatched to all link maintenance teams for immediate incorporation. Helping the USA It was during the Cold War that the West listened to domestic radio programmes from countries under Russian control, but the USA Embassy in Vienna was having difficulty in monitoring one transmission due to a high level of jamming from a Russian transmitter. A request came to the BBC via Bush House for a special receiver capable of receiving the transmission, and the frequency was specified. I was asked if I could help so I designed a receiver with a tuned ferrite rod aerial, as well as 10.7MHz crystal IF filters to give a sharp skirt loss. The ferrite aerial positioning enabled rejection of the jamming transmitter if at a different bearing to the signal source. This special test receiver was constructed and sent to the American Embassy in Vienna. About a year later I asked how the receiver was performing and if the embassy still needed it. A couple of months later the receiver was returned to Designs Department with a copy of an Embassy Internal Memo attached. It reported that using the BBC receiver reception was satisfactory and 'Was such a receiver not available State Side?' A subtle appreciation from across the pond! 2LO to the rescue In 1989 the Electro Static meter was borrowed from 2LO (with the E.i.C. permission) and used to measure the output voltage from the Cockcroft Walton multipliers in a pair of Quad Electro Static Loudspeakers. The meter gave the correct reading (about 6KV) at infinite impedance where normal 0.01mA meters were an excessive load. The 50Hz coupling capacitors in the multiplier being only 10nF. Just shows the quality of E.S. Meter equipment available in those early days. The Quad Loudspeakers belong to Les Rottier. It IS broken - so don't fix it! When I started work at Designs department I was not familiar with all the facilities and test meters in use and I happened to pop a moving coil meter. I phoned through to Equipment Department Coil Winding section and asked for some 48 SWG wire, but I was told that the department had not used wire beyond 40 SWG. I therefore had to rewind the meter using the existing wire. I was lucky and the repair was accurate and with normal meter movement. Tom Worswick found that I had repaired the meter and I was told that at the BBC one did not repair test equipment, but to buy new and discard the broken equipment! Oiling the works In the R.F. section at Designs Department I designed Very High Frequency (FM) and Medium Frequency (AM) receivers for mounting in the Imperial Chassis CH1/12A. For Local Radio monitoring signals the flat audio response to 8KHz on Medium Frequencies was appreciated. The laboratory prototype chassis required a metal screen to shield it when mounted in a bay of other units, so I included a tin cover in the design. The Metalwork Section said that they did not have any sheet tin of suitable gauge and the cost of a sheet would be excessive for the one screen ordered. I suggested using a gallon can as used for oils and cleaning liquids. 'The BBC does not use second hand materials!' I was told. However, an empty tin of thinners was cut open and the paint removed to find that originally it was a Castrol tin of oil! The resultant tin screen produced was an excellent fit and provided Electrostatic and Electromagnetic screening within the confines of the Imperial dimension system. The cost of the screen in production was small. New: Multi-coloured chassis could be electrifying!Designs Department produced many designs of passive and active equipment and there was a need to have a set of standard chassis units that plugged into a 19 inch rack mounted crate. In the 1950's and 60's the chassis were of aluminium construction with Imperial dimensions and they had grey painted front panels. Over the years, when new facilities were added to existing installations this usually involved placing new grey-fronted panels near to existing ones and it was noticed that the hue of the front panels changed with production batches. It was eventually decided that the colour white had the least change of hue with manufacture and the colour of the front panels was changed to white. In about 1973 (?) a new chassis system was designed and it was called "BMM" which stood for Binary Metric Modular. This was a great improvement on the old grey/white Imperial system and great care was taken to specify anodised aluminium front panels which gave a uniform appearance. The BMM system was also safer. The old Imperial chassis had a metal spike on the back which which was used to locate the unit in the correct position in the crate, and it also often made use of a multi-way connector that provided a feed of 240V mains. If the unit was seriously mishandled when inserting into its crate then the spike could touch the mains connector socket and give a shock to the handler. Collectors of very old BBC units beware!
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