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FAQ (Frequently Asked Questions)

The Chain Home Low radar system

Radar Type 2 (CHL)

Radar Type 2 (CHL) 185 foot tower (photo - "Watching the Skies")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!

detail from the photo above, Radar Type 2 (CHL) 185 foot tower (photo - "Watching the Skies")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!

 

 

 

Frequency

200 MHz

Tx peak power

150 Kw

Tx pulse length

3 us

PRF

400 pps


 

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Updated 31/10/00

Constructed by Dick Barrett
ęCopyright 2000 - 2005 Dick Barrett
The right of Dick Barrett to be identified as author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.