In 1948,
Claude Shannon used his recently introduced science of
information theory to study
radar systems and suggest that there were calculable fundamental limits to their performance. This was unexpected, and provoked wide interest in the radar field. In 1949, the
Telecommunications Research Establishment (TRE), the
Air Ministry's radar research arm, began applying this new concept to consider the extraction of both location and velocity information from a radar signal, and to the expected performance of long-range radars against low flying aircraft and the detection of
submarine snorkels in rough seas. The work was interesting enough that the
Ministry of Supply funded further development under the
rainbow code "Orange Poodle". The system operated in the
shortwave region, at 13 m wavelength. The signal was sent in-phase into a series of vertical antenna elements, and on reception, it was separated through its
Doppler shift into bands of ⅓ Hz. For experimental purposes,
Marconi built a smaller version with eight elements that was constructed by connecting them to one of the disused
Chain Home antennas at
RAF Downderry in
Cornwall. This mounting meant it could point only in one direction. Experiments began in September 1952, and found reasonable results in spite of interference from local shortwave sources. A larger version consisting of 32 elements strung between two towers was completed in January 1953, and underwent testing in February and March. Sea clutter was completely absorbed in the lower frequency receivers, and aircraft were easily detected in the higher frequencies, corresponding to faster movement. Signal strength turned out to be even better than expected because scattering off the
troposphere added to the signal. The tests were very encouraging and led to plans for a production version that might be part of the
ROTOR network. However, by the end of the year development had been cancelled when it was pointed out how easily the system was interfered with by local shortwave sources; an enemy could easily jam the radar using low-cost commercial transmitters while still well below the horizon. ==See also==