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CHANGE IN THE ETHER

At this point, its important to realise how pivotal Thermionic Valves were, for a revolution and growth into the wireless industry; between the wars of 1914 to 1940, produced rapid valve development and understanding, of there primary electron principles.

Valve design pre-1914 is attributed to many scientists, but Fleming's valve with two electrodes based on the Edison effect, was first used as a replacement for the wireless crystal detector, the "gallium mineral" to be called a diode, and produced considerable sensitivity to detect weak signals. This very practical discovery allowed further development by the Marconi Company, and others, who saw the potential future in Electronic Thermionic Valve Technologies, to produce with greater efficiency wireless science, from an Electro-Mechanical discovery of the primary physics.

Individuals with a knowledge of valve techniques, e.g. the "R-Valve" had far better reception results through amplified T.R.F... Tuned Radio Frequency method: the idea was to use one or more "tuned amplifying stages, coupled together" to increase a receivers sensitivity and, it's selectivity when tuning in a signal. The down side was, its inability to tune large area's of the band: however this design became a standard line-up concept before the discovery of Super heterodyne techniques...
This method used a local oscillator that usually beats above the wanted station signal; the result would produce a difference in the two frequencies, e.g. local oscillator and receiving frequency produced a third beat frequency called, the I.F... one or more Intermediate Frequency amplifiers could then be used to increase the receiver sensitivity, and made continuous tuning possible with highly selective station location; it also restricted any near-by stations, that were not required.

However, this design only came into use after the second world war; thus, T.R.F. as a receiver tuning system, was the only known design technique used in the early 1939, 405 Line Television receivers, until after 1945 where, the need for Super-heterodyne techniques was required, to provide multi-channel station selection.

Further to the wireless activities of these early years was Mechanical Television; John Logie Baird developed a 30 line system in 1926, and proved the overall working technical feasibility, to send Vision signals at first through wires, and then by wireless transmission. In the Jersey Evening post December 1926 edition, under "Wireless Notes" by Jack Broadcaster ! his article stated that 'the first television transmission licence was requested by, J.L. Baird"... the Post Office was somewhat nonplussed by this request, being the first ever licence for television, and duly awarded a licence to transmit on 200 metres in the long-wave band, using an appropriate call sign of, 2TV.

Eventually, the government instructed the BBC to adopt the J.L. Baird system in its experimental - form, with transmissions late at night. The reason for the late night transmissions was that, the BBC were not too pleased being told to adopt the early 30 line television system, and thought it had not developed enough in picture quality. If you were able to listen-in on the wireless, the signals from the Baird 30 line mechanical system, produced a rather low buzzing sound a bit like a honey-bee, in flight. This sound was the vision signal changing between dark and light, with a 3% Quasi Line Breaking Pulse, for the motor to keep the 30 hole disc speed synchronised, with the image.

The picture was postage stamp size, magnified up with a lens for viewing. The BBC studio camera had a drum with 30 mirrors around its surface, rotating 750 RPM; this formed the sequential image raster being televised. Baird initially ran the service at his own expense, and despite considerable development, the mechanical system was terminated on the 11th of September 1935, in favour of the
all new valve EMI 405 Line system.
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A Recollection of Jersey's Radio & Television Industry 1922 - 2002  By Brian M. Lucas
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