The underground radar installation at Ventnor consisted of the Radar Office, Track Telling room and Radar Cabin. There was also a small workshop and rest facilities.
Master Trigger Unit - generated and distributed sync pulses to all the station transmitters and displays, video map and range mark units.
Bulk Power Supply - supplied unstabilised +400v, +250v and -300v to console 64s.
Negative Reference Unit - supplied -500v to console 64s.
Video Map - supplied coarse and fine map signals to overlay the radar signal display on all console 64s
Head Selector Units - Facilitated remote channel switching from console 64s
Built in Monitoring Unit
There would also have been racks for 45Mhz IF amplification (normal and narrow band), time base generators, resolvers for converting the turning information from the radar heads into sine and cosine waveforms and range mark generation. Another unit would have supplied -50v for general relay operation.
On the mobile side, I remember the 'Test Rig 6', which was an early version of a supermarket trolley. It had sprung rubber tyred wheels and two vertical handles on the front to one of which was attached a sprung trigger handle which, via a Bowden cable, released the brake. The trolley contained a display unit and a Test Set 402 which was designed to supply any test signals required to service the consoles. At the rear were a number of coaxial leads terminated with F & E plugs which could be used as required.
Track Telling Room
If I remember correctly, there were five PPI console 64s and two height finder console 61s here. The 61s were quite an old design and mainly autonomous but the 64s were state of the art and derived most of their supplies from the radar office.
There was also a Kelvin Hughes photographic display unit in a sunken area at the far end of the room. I believe the electronics for this were similar to the 64s, but I was on leave when the PDU training took place and cannot confirm this.
There were two console 64s in here with R/T facilities available.
MORE DETAILED STUFF
The Master Trigger Unit had a crystal oscillator which fed the trigger to a number of delay units. These were individually adjusted to compensate for line lengths to various heads in order to ensure that everything fired together. The outputs were via a cathode follower to deliver a low impedence pulse down the lines. I think the basic P.R.F was 250 but there may have been a facility for 500 too.
The Bulk Power Supply had six large rectifiers which could be seen through a Perspex window in the door. When the unit was powered up they had a slightly mauve appearance and looked quite formidable. Unless local control was selected they came on when an operator switched a console on.
The Video Map was an exception to the general rule inasmuch as it had its own + and - H.T. and 15KV E.H.T. supplies and timebase It was manufactured by Horstman of Bath and had a heavy cast gate containing the CRT and optical system. A selsyn at the bottom of the hinge drove a shaft which ran up to the top and connected with 36:1 gearing which in turn rotated the CRT deflection coils. To ensure that the coils were in synchronism with the aerial a system called auto align was used. This shorted two windings in the selsyn causing it to be magnetically braked until the aerial came round into the corresponding position, when a -50V pulse from the aerial released the short and allowed the selsyn to turn. ( in practice it was quite tricky to set this up, and could result in the selsyn taking off towards destruction! ) The quick removal of a Jones plug was required to put this right.
The CRT had a special phosphor in the U/V spectrum which was focussed through two parallel lens systems and glass slides on to photo electric multipliers. These were very sensitive to U/V light and were kept wrapped in wadding to keep them dark when not in use. We used to turn off the overhead lights when we were fitting them. The coarse and fine channel signals produced went to the Head Selector Unit for remote selection by the operators as required.
The Head Selector Units were very chunky pieces of equipment weighing about a hundredweight each - very hernia making! There was one for each console and they handled pretty much everything that was required by that particular console in the way of video, X and Y deflection, range rings, video map, radar bright up (3000 microseconds +2V for 250 PRF) and inter-trace bright up pulses (1000 microseconds +2V for 250 PRF) On the top of the unit there was a horizontal shaft connected to a small motor in the centre and along this shaft at regular intervals were wafer switches. The motor would turn as requested by the console operator and the appropriate signals be routed through. The rear of each unit was covered with a mass of F&E sockets for taking the signals away.
The Type 64 console had the minimum of circuitry. Voltages from the radar office were stabilised to provide +250V and -300V. There were no rotating deflection coils as resolved sine and cosine sawteeth were fed to deflection amplifiers (Type 313 RH amplifier for X deflection and Type 314 LH amplifier for Y deflection) - both these amplifiers were identical and fed appropriate current waveforms to the deflection coils during the trace period and intertrace period. Trace expansion enabled particular parts of the display to be examined in greater detail and off centring (up to 200 nautical miles) allowed any particular region of interest to be brought to the centre of the screen and this remained centred for all degrees of expansion. The intertrace period was used for drawing strobe markers on the screen e.g azication. The operator could use a knob which was sprung in both directions and which would swing a height finding aerial round clockwise or anticlockwise to the required bearing. He could also alter the range of the azimark which supplied two bracketing marks to the console 61 As the aerial moved to the desired position the H/F operator was able to obtain the required height.
Type 893 used by interceptor controller
Facilities: Height finder laying control
Range strobe/azication marker
Video map and range rings
Type 894 standby azication console in intercept cabin
Facilities: as Type 893 plus
Intercom call light
Type 895 track telling consoles
Facilities: Head selector
Type 896 azication positions in track telling room
Facilities: as Type 895 plus
Height finder laying control
Type 897 used when height finding control was not required and when azimark was to be used for synchronising purposes.
Facilities: as for type 896 but with less height finding laying control.
All desks contained mains on/off switch, heaters on light and HT on light.
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Text © 2006 Mike Powell