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Bedell's End

Page history last edited by Alan Hartley-Smith 3 months, 3 weeks ago





Currently the site indicated as Bedell's End in a company brochure now lies adjacent to a recently installed roundabout beneath an arable field - a length of tarmac path close to the hedgerow is the only surface indication that structures once stood here


Originally an HF/DF ‘Y’ station it was described as an Interservice Research facility. Located on the western edge of current Chelmsford a few 100m north of the A1060 Roxwell Road the site was one of the original war time ‘Y-stations’ where British Signals Intelligence collection and receiving sites operated by a range of agencies including the Marconi Company. There is now a considerable record of this period here


Also the site was used to house an AMES Type 7 radar installation. Later Marconi was engaged in the development of L-band, 23cm wavelength radar, for the RAF including a clutter rejection system. To support this work the first experimental model was built here. Being located in a saucer shaped depression, the site topographically proved to be too good for testing the equipment against permanent echoes and a new site was developed at Bushy Hill, near South Woodham Ferrers. Bedell's End, nevertheless, continued in use for some DF work. The radar site was closed.


Two clusters of huts were spaced along a track into a cornfield off Roxwell Road opposite the road down to Writtle. in 1956 one set of two housed two engineers (Bob O'Neill and AH-S, with occasional visits by George Slack) and a handyman and was half a mile up the track from the road. At that time it was in use for Type 7 Modifications and for designing metric naval radars.


The other huts were at the junction of the track and Road, and at that time the engineers there dealt with HFDF. However there has been an input recently about a later use: 


Recent input from Barry Pettican

As I recall the huts were weather boarded and I assumed they may have been constructed and used during WW2. I joined the Research Division in 1967 and because I had specialised in Control Engineering with Electronics I gravitated towards the Servo Section. Most of the development for Goonhilly 2 as it was called, had been completed but there were, as usual, a number of issues arising during the site work-up and setting to work. 


When I first went to Bedells End two of the main servo drive motors were installed in the hut on a test bed.  The azimuth axis motive effort  for the Goonhilly system comprised two sets of two motors driving wheeled bogies on a railway track. Each motor pair was connected via a differential gearbox. They were basically d.c motors fed from a three phase supply with thyristor bridge controllers. As I said previously I believe they are still in occasional use on the Goonhilly site but I am sure BT could confirm. 


The hut had a 415volt 3 phase supply and this is why it was chosen for the test bed. The drive motors had several means of control (e.g.variable velocity slewing - it has to be quite a slow on a 90 foot dish!- as well as very accurate position control.  In the case of the latter, it was evident from site that when stationary (as a synchronous satellite tracker was for much of the time) there was a small amount of movement caused by wind forces on the dish back-driving through the gearboxes (backlash). The motor brakes were obviously not effective in taking this out.  


Ernie Hoare and I came up with an idea which involved counter-torquing the two pairs of drive motors. (effectively applying a small opposing drive to each pair) the gears were always in mesh and this removed the tendency for the dish to move slightly when it was supposed to be stationary.   All of this was initially tested out at Beddells End using the pair of motors and drives we had at our disposal. Later Ernie, Mick Cranmer and I spent some time on site, testing and demonstrating these servo performance features to the (then) GPO.


There was not much else in the hut I was using at the time.  Obviously there were work benches and test gear. I believe there was another development marine radar drive system (AMPD?) also in situ at the time. That did not require 415 volt. 3 phase but reduced the space required at Guys Farm. 


So in summary that particular Bedells End hut was used as  a high power testing extension of the Servo Lab at Guys Farm. It was a very pleasant place to work when I was there for a short period in the early summer of 1968.


The site was also known as Hodges Farm (whose land it was) and had been a DF station during WW2.  See Pastscape




This is a typical Type 7 array - the one at Bedell's End had an extended top section. In this instance only the turning gear was housed below the array, the Ward Leonard motor/generator with its controller, the transmitter and T/R switch being in the adjacent hut. Tensioned open-wire feeders were strung horizontally across the space to a stub-isolated vertical set inside the stationary column. There was a ladder to gain access to the rotating cabin at top. Inside this the feeders terminated at flat-ring stator plates of the capacity switch, the rotating plates then taking off the power to the array feeders. Doing low-power standing-wave testing in there was quite interesting!


If you would like more detail about this setup see here


Its later use for 23cm work is shown in this recently discovered picture, with waveguide feeds in evidence, being used for clutter rejection experiments.







Comments (1)

Ian Gillis said

at 4:29 pm on Feb 10, 2016

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