Watson Watt discussed the problem with his junior colleague,
Arnold Wilkins and asked for more calculations to be done. It
was Wilkins who also introduced the point about some earlier
(1931-2) problematical observations that Post Office engineers
had noted. There had even been a report written on the subject
(GPO Report No 233, 'Interference by Aeroplanes').
The engineers had observed disturbances to VHF reception
when an aircraft flew in the vicinity of a radio receiver
and Wilkins wondered if this phenomenon could be used to detect
the presence of aircraft.
In a lengthy memo to the Air Ministry, he suggested that
it should be possible to locate the range, height and bearing
of an aircraft on a wide front up to a range of 100 miles
using
" the Radio Echo method". This was the 'trigger'
that was needed to start the Government machine in motion.
He later stated that there would be a need to construct a
'chain' of transmitter / receiver stations all along the coast
to protect the British Isles.
He also suggested that 'friendly' aircraft could be identified
using the same system.
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