The period from May 1940 to March 1942 was arguably the most fertile
period in the quest to produce airborne radar that could be employed
for offensive purposes. TRE Worth (and the associated Leeson House)
were after all, primarily Research establishments although operational
CH and CHL work was also carried out there.
It was also the period when Britain was under severe duress; the
evacuation of Dunkirk, the Battle of Britain, the Blitz and the
Battle of the Atlantic tested the nation's resolve to the limit.
The experimental CHL unit at 'D' site was soon spawning new devices;
C.J.Banwell developed a special transmitter switch that soon allowed
a single aerial to be used instead of two. Then a rotating device
(at first manual and then electrically driven) was conceived. These
two developments allowed Dummer and Franklin to perfect a rotating
time-base display layout on a cathode ray tube. Hence GCI coupled
with the new Plan Position Indicator
was the first major achievement at Worth. Although too late to help
during the Battle of Britain in the summer of 1940, GCI and PPI
were essential operational tools for all the Armed Forces from late
1940 for the remainder of the war.
New aerial designs
for both ground, airborne and shipborne uses were developed at this
time. Perhaps the greatest step forward came in July 1940 when the
first prototype Magnetron arrived. With this invention it was possible
for Bowen's centimetric team to forge ahead with more effective
and accurate Airborne Interception (AI) equipment. In August 1940,
the team produced the first 10 cm echo from a building: the old
chapel at St Aldhelm's Head.