The DEHS Russell Burns Spring Lecture took place on Wednesday 30 May 2018 at the Steam Museum, Fire Fly Avenue, Swindon, SN2 2EY.
The DEHS was delighted that this year’s lecture was given by Prof. Simon Watts, MBE, DSc, FREng, Visiting Professor in the Dept. of Electronic and Electrical Engineering at the University College, London on UK Maritime Surveillance Radars for the RAF, 1950–2010.
Until 2013 Simon was deputy Scientific Director and Technical Fellow of Thales and has worked on a wide range of radar and EW projects. He is author and co-author of 80 journal and conference papers, a book on sea clutter and several patents. He is a Fellow of the Royal Academy of Engineering, the IET, IMA and the IEEE.
Registration was from 10.00–11.00 and were followed with half-hour lectures by the DEHS President, Keith Thrower OBE on ‘Frequency synthesis in military radio communication’ and by Peter Butcher, Editor of Transmission Lines, giving a survey of batteries in military radios. Prof. Simon Watts’ lecture followed after the lunch break.
The Steam Museum is located at the Swindon out-of-town shopping centre which has a very large car park close by. Parking is not permitted at the museum.
Synopses of the three lectures are given below:
UK Maritime Surveillance Radars for the RAF, 1950–2010
Prof. Simon Watts
The history of airborne radars developed in the UK for long-range maritime surveillance by the RAF spans from 1940, when ASV Mk. I entered service on Sunderland and Hudson aircraft, through to the 1980s, when the Searchwater radar entered service on the Nimrod MR2. This history came to an end in 2010 when the Nimrod MRA4 programme and its new radar were cancelled and the Nimrod MR2 was taken out of service.
This talk will concentrate on the development of ASV radars in the UK after WWII. Following early work at VHF frequencies with ASV Mks. I and II in 1940, the development of centimetric ASV radars based on H2S (ASV Mks. III, VI and VII) paved the way for the early post-war systems. With the introduction of the first dedicated maritime reconnaissance aircraft, the Avro Shackleton, the ASV Mk. 13 radar was developed. This radar was replaced by the ASV 21 in 1959. The Nimrod MR1, fitted with the ASV 21D radar, took over from the Shackletons from 1970. In 1980 the Nimrod MR2 with the Searchwater radar was introduced. ASV 13 and ASV 21 were magnetron radars that were still based on the techniques developed in WWII. However, Searchwater was a completely new concept, having a high power wideband TWT transmitter and being the first generation of ASV radars to include modern signal and data processing (digital as well as analogue) and able to automatically detect small targets in the presence of strong sea returns.
Frequency Synthesis in Military Radio Communications
From the early days of military radio communication frequency stability and accuracy were always a problem. This problem became even greater with the expansion into higher frequency operation into the HF, VHF and UHF bands. A solution came when quartz crystal oscillator became available. For reasons of cost, however, it was only feasible to have one or just a few selectable channels.
For wide-band tuning, where crystal oscillators were not possible, the problem of frequency stability became more acute, particularly when single sideband operation was introduced, where the stability required was better than 50 Hz.
The solution to these problems was found in the 1950s when radios were designed with external or in-built frequency synthesisers where channels could be selected in small increments across the whole band of operation and where each channel was derived from a single, highly stable crystal oscillator.
This then led to the introduction of improved surveillance receivers where it was possible to switch rapidly through a large range of channels and to analyse the content of the traffic.
A further development was frequency-hopping radios which switched through a range of frequencies using a pseudo-random algorithm, protecting the radios from interception and jamming.
Short Survey of Batteries in Military Radios
The history of battery technology has largely responded to the requirements for portable power. The earliest cell used, the Grove Cell, was invented in 1839. This had a zinc anode in dilute sulphuric acid with a platinum cathode in concentrated nitric acid. The Grove cell was extensively used in telegraph work and for fusing mines, since it had low internal impedance and a higher voltage (1.9 V) than other contemporary cells. However it discharged poisonous nitrogen dioxide in use.
The emphasis has been to make higher capacity, smaller and safer batteries. Possibly the most familiar and most used cell was invented by Georges Leclanchè in 1868. It used a carbon rod cathode surrounded by manganese dioxide and powdered carbon, with a zinc anode and ammonium chloride solution as the electrolyte. The big advance was made by Dr Carl Strasser who constructed the first ‘dry’ Leclanchè cell, a battery still in everyday use today.
The advent of radio communications demanded both low voltage batteries for filament supply and high voltage for anode supplies. As applications of radio became widespread, the provision of high voltages made the high tension battery too bulky and other methods of supply became necessary. Propeller driven generators for aircraft high voltage supplies, rotary converters and the vibrator power supply were developed.
Different chemistry overtook the Leclanchè cell for primary batteries and the lead acid cell for secondary batteries, largely driven by military requirements. Primary cell chemistry moved to alkaline manganese dioxide and latterly to lithium. Secondary cell chemistry progressed from lead acid to nickel cadmium, then nickel metal hydride and finally to lithium Ion.
For many years the development of fuel cells was pursued, especially for use in space and today a simple, cheap fuel cell is in everyday use, the zinc/air battery.
Finally, no review would be complete without discussing the most difficult battery requirement–that of the battery developed for the artillery shell proximity fuse.