The Chain Home Low radar system
Type 11 (CHL/GCI)
In an effort to avoid enemy jamming the Type 11 was designed to operate in the same band as German radar equipment. The performance of this radar was somewhat disappointing though, due mainly to a large gap in the vertical cover that could not be removed by tilting the aerial. Some improvement in the performance was gained by digging out the ground on which the trailer stood in order to lower the aerial!
Early models featured twin truncated paraboloid aerials with a 4.5o beam width. The transmitter consisted of a pulse amplifier chain and had a coherent output. The Mk VII version produced a peak power of 50 Kw, with a pulse length of 4 us and a pulse repetition frequency of 500 pps. Performance was limited to around 60 miles on a medium bomber sized target.
(Source - "Watching the Skies")
Constructed by Dick Barrett