The Chain Home Low radar system
Radar Type 2 (CHL)
The Chain Home (CH) system had significant gaps in its low level cover and so to combat this deficiency the metric Type 2 Chain Home Low (CHL) was developed from the CD (Coastal Defence) radars that were first installed to detect coastal shipping in 1939.
The early equipments had separate transmit and receive aerials and cabins which were rotated synchronously. Several methods of rotation were tried out; some aerials were cranked around by hand whilst Gordon Kinsey describes another method in his book "Bawdsey - Birth Of The Beam":
"Wing Commander Kenneth Mummery remembers that the new system had its drawbacks as well as its advantages:
"Several mechanical problems were encountered during the early days of C.H.L. stations, as the narrower beam aerial array had to be rotated in order to sweep or scan, and many novel methods were devised to obtain this movement. One remembered by many was a framework not unlike that of a bicycle frame, with handlebars and seat, chainwheel and pedals which, when they were turned, rotated the aerial through a series of gears and links. A joke enjoyed by the 'informed' was that one could always identify one of the W.A.A.F. R.D.F. operators by her bulging calf muscles and unusually slim figure.""
Fortunately for the ladies power turning was introduced in April 1941!
The production models comprised of one common transmit and receive aerial that was made up of a 5-bay, 4 stacked dipole array mounted in front of a reflecting screen. The array could be rotated at 1, 1.5, 2 or 3.33 rpm. An impression of the size of the aerials can be gained from examining the detail from the main photograph; someone can be seen standing in the doorway at the bottom left hand corner of the detail!
Constructed by Dick Barrett