 A
60-kW tetrode valve, another outcome of C. R. Burch's work, was in
operation with the G.P.O. when the head of the radio department at
the National Physical Laboratory, R. A. Watson Watt, was starting
his experimental station at Orfbrd for work on radio direction-finding
(r.d.f.), later known as 'radar'. One of his first difficulties was
the production of stable high-frequency radiation at very high power,
An experimental transmitter had been built in the Company's research
department to find the minimum operational wavelength for the tetrodes,
and Watson Watt was invited to see tests carried out on these valves,
which were delivering to an aerial a power of more than 100 kW at
55 Mc/s.
As
a result of his report the Air Ministry asked the Company in October
1936 to quote for a number of valves and also accepted an offer
of assistance in the design of their transmitters. In the following
March, M-V was initiated into the r.d.f. programme, and work started
immediately under the technical supervision of J. M. Dodds on the
design of the CH (chain home) transmitter. On June 11 there came
a verbal instruction to proceed; in July a contract was placed for
two transmitters, and in November it was increased to cover forty
transmitters, the whole of those required for the early warning
system for the air defence of Great Britain. Each transmitter was
to incorporate the Company's continuously evacuated valves, which
were the only ones that could give the high powers necessary at
the wavelengths required. This was the first of many war contracts
for all sorts of radar equipment.
Much
of the research work of this period was rendered possible by the
use of continuously evacuated high vacuum apparatus, which itself
was due to one of the many discoveries made by C. R. Burch in the
M-V research laboratories. In 1933 however, Burch left the Company,
having accepted a Leverhulrne fellowship in optics at the Imperial
College, and three years later he moved to Bristol University, where
he is now a fellow of the H. H. Wills physics laboratory. In March
1944 he was elected an F.R.S. on account of his contributions to
science especially in connection with the obtaining of high vacua.
MATERIALS RESEARCH
Important though less spectacular was the work carried out on properties
of magnetic materials, and the subsequent investigations on machines
and transformers. For example, methods were developed for measuring
pole-face losses in rotating machines and stray losses in transformers
and, under F. Brailsford, for the direct measurement of rotational
and alternating hysteresis loss on small specimens. The preferred
orientation of crystals, particularly in the newer cold-rolled silicon
transformer steels, was determined magnetically.
Crack
detection work resulted in the development of apparatus suitable
for routine testing, and by 1934 the requests from other firms were
leading to the manufacture of magnetic crack detection equipment
on a small scale. A consulting and inspection service was organized
for industrial use. Non-destructive methods were also developed
for testing non-ferrous metals, for example a fluorescent method
which can be applied to practically every material.
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