Alan Dower Blumlien

1. Alan Dower Blumlien • A forgotten British Genius • Born 29th June 1903 Hampstead London • Died 7th June 1942 in a wartime air crash

2. The Last Flight 7th June 1942 A Halifax aircraft carrying 11 crew and scientists on a test flight to examine H2S radar crashed killing all on board. • Churchill said this loss was the greatest disaster to befall ‘the secret war’ • This loss was hidden in secrecy for many years

3. Back to the story • Alan Blumlein came from a wealthy family and although interested in electricity and steam trains was a slow starter, not learning to read and write until he was 12 • In 1914 his father died and this shock started Alan’s drive for education.

4. Schooldays • Alan won a scholarship to Highgate Grammar School which had a strong bias towards science education. • He then went on to the City & Guilds college where in 1921 he gained a first class degree in heavy engineering

5. Early Career years • In 1924 Blumlein joined International Western Electric, (later STC) where he defined the amplitude/frequency response of the human ear and designed the first weighting networks.

6. First publications 1924/5 • He published IEE papers on high frequency resistance measurements. • This won him the IEE Premium Award for Innovation. • Later he wrote seven articles for Wireless World.

7. STC in Switzerland • STC were having problems with noise pick up on the telephone lines that ran alongside the electric railways Blumlein and a colleague were sent to investigate the problem and designed a form of loading coil that reduced crosstalk and remained in use until the end of the analogue phone era.

8. STC to Columbia- 1929 • Blumlein left STC in 1929 for the Columbia Graphophone Company where his first task was to break the Bell Labs patent on disc recording. • This was the ‘Western Electric Moving Iron Cutting Head’ on which royalties were paid.

9. The Moving Coil Head • Blumein’s moving coil cutting head changed recording from ‘Hill & Dale’ to side to side. • This change broke the patent, improved sound quality and introduced weighting of the cutting signal. • The patent included a sapphire cutter & acetate masters.

10. 1931- Mergers • The Columbia Graphophone Co. and the Gramophone Co. merged to become EMI with research facilities at the new site of Hayes. • Blumlein joined the new EMI research department on November the 1st

11. EMI • An early task at EMI was the moving coil microphone, Blumlein’s designs were used at the studios of EMI at Abbey Road and at the BBC at Alexandra Palace. • The new microphone led to the next big idea.

12. Patent No.394325-14/12/1931 • ‘Improvements in, and relating to Sound Transmission, Sound Recording and Sound Reproducing Systems’. • This patent made 70 claims, these include • Coincident pairs of velocity mics with their axes at right angles (the Blumlein Pair)

13. The Big Patent 1931/2 • A stereo cutting head, with L&R signals on opposite walls of the groove. • Hybrid transformers to allow sum and difference signals • Circuitry to blend spaced mike signals to preserve spatial information, the ‘Dummy Head’ technique

14. Binaural Sound (Stereo) • The first stereo discs were cut in 1933, but much of the work was intended for cinematic use, where records synched to the projectors were commonly used. • Some of the early test films are still in existence. While sound was important at the end of 1933 Blumlein moved on to the next challenge.

15. 1933 Television Baird & EMI • Blumlein’s television patents include Resonant Fly back scanning no.400976 • Improved power supplies no.421546 • Black level Clamping no 422914 • During this period Bairds mechanical scanning was the leader but could never compete on resolution or brightness

16. TV Baird Marconi and EMI • Competition in the technology of TV was fierce with mechanical and electronics competing. In 1936 Baird’s improved 240 line system began transmissions from Alexandra Palace • EMI had a studio and transmitters on the same site and the two systems played on alternate nights.

17. Blumlein and Alexandra Palace • His involvement in TV was immense, with patents on improved Coaxial Cable, the design of the 45mHz power amplifiers, Slot Radiator Aerials and the circuit, that is known as ‘long tailed pair’

18. EMI-Marconi and television • Between 1934 and 36 The engineers at EMI and Marconi built the electronic TV system from scratch, Blumlein was in charge of the electronics team and filed over 60 patents during the 14 month period possibly the most important, the divider chain that gave the 405 line system.

19. Broadcast TV • After a period of competition between electronic and mechanical systems in 1937 the government chose the EMI 405 line over the Baird 240 line and the tv service started in earnest.

20. 1936 a war looms • Robert Watson Watt had observed the flutter on the Alexander Palace transmissions caused by aircraft and the concept of RADAR was born culminating in the Chain Home early warning system.

21. 1938 Sound detection systems • Blumlein designed a sound detection system based on his stereo work, the positional information displayed on a CRT, these were used extensively during 1940 and 1941. • EMI were however excluded from most war work as they were regarded by the military as an entertainment company.

22. Radar • Chain Home could warn of approaching aircraft but all too often the fighters could not find them, eventually EMI were let into the club and the development of radar. • The big problem was getting bombs onto targets many raids missed by miles Ground scan radar was needed

23. EMI Blumlein and H2S • During 1941 Blumlein and his EMI colleagues were part of the team that were given the task of developing H2S ground scan radar • Research was based at TRE establishment in Gloucestershire

24. The last day • On June 7th 1942 a test flight carrying all but 2 of the H2S team and the most experienced flight crew took off for a test flight, the H2S team leader Bernard Lovell and one technician were the only ones not on board. • The aircraft crashed as a result of a preventable maintenance failure.

25. After the crash • Part of the invisibility of Blumlein is down to the air crash, H2S was so secret that the loss of the plane and the deaths of those involved was kept hidden. The names of those killed were given out over several days hidden in other casualty lists.

26. Alan Blumlein • During his working life Blumlein produced 128 patents covering telephony, television, radio transmission, sound recording key design features in television cameras power supplies and amplifiers