Purchase tax was increased to 66.7% - the second rise in little over 6 months - and not suprisingly met with much outcry from both manufactures and the public alike. I suspect this was in an atempt to discourage the home market in favour of exports, the revenue from which the country deperately needed.
Figures for monthly prosecutions of people failing to have purchased an appropriate broadcast license typically ran at around 250-300 per month across both radio and television. By comparison, in Australia nearly a quarter of a million people rushed out to buy a broadcast license when the Australian government anounced they were about to clamp down on license dodgers.
In a report issued at the start of the year by B.R.E.M.A. it was stated that the main limitation against increasing television production was the shortage of C.R.T.s. At the time C.R.T.s were manufactured manually and it was the shortage of the highly skilled glass blowers that was restricting C.R.T. production. Whilst automated equipment was a possibility, it would require large orders before such equipment could be economically installed.
In April, GEC began field trials for a television radio link along the proposed London to Birmingham route .
This year there was no Radiolympia. The reason given was to enable the industry to concentrate on production for its export targets as well as allow more time for the development and production of new sets. However there were many other exhibitions during the year which would feature both radios and televisions.
Possibly the first was the Ideal Home Exhibition which opened on March 2nd, amogst whose exhibits was the HMV1901 combined TV and radiogram.
In April Olympia was presented with roof-top aerial, maintained by the Radio industry Council, to ensure the best possible reception for any televsions that may be on show at any events. This was of great benefit for the British Industries Fair which opened at Olympia in May andwhich had many televisions on sale including the HMV1901, Sobell T87, Ekco TSC48 mirror lid set and McMichael's first post war television.
Whilst Pye's 1946 model B16T established Pye's technical lead in domestic television, far more technically important was their B18T model released in 1948. Up to this point all televisions required an A.C. mains supply since a transformer was required not only to provide the very high EHT voltage required by the CRT but also to provide a supply high enough to enable the scanning coils to be driven quickly enough using the valves then available (valves specifically designed for TV use were yet to appear in any number). The mains transformer was necessarily large and expensive, and had to be carefully positioned such that it's magnetic field did not interfere with the scanning of the CRT. The B18T's solution was three fold ; first the EHT was generated by rectifying the high voltage pulses generated across the (line) scan coils. Secondly, energy recovered from the scan coils during this flyback was used to "boost"the HT supply used to scan the coils. Finally, all of the valve heaters had to be connected in series, a challenge given that specialised valves with the necessary heater-cathode insulation had yet to be introduced.There was little room accomodate any reduced mains voltages and indeed operation at a reduced 190v-220v AC (supported by almost all other manufacturer's sets) required the adition of an auto-transformer costing an additional £1 5s.
Thus the B18T was the first set that no longer required a mains transformer. This had an accidental side effect - it became the first set that could also operate directly from DC mains (still in use by many households) although this had not been the original design intention and indeed the manufactures initially never advertised the set as anything other than for AC supplies only. Pye did, however, subsequently make some very minor modifications to better suit D.C. operation.
|The Baird T163
Probably the first set designed for
both A.C. and D.C. operation.
|The Pye B18T
The first set capable of operation from
D.C. supplies - but not by design !
The B18T's design features were not original - the idea of rectifying the line scan voltages to develop EHT had been developed in Germany immediately prior to World War II, and the basic principle of recovering energy from the scan coils had been covered in a British patent as long ago as 1932 (albeit using a different circuit). But nevertheless, it was still Pye who produced the first commercial implementation of these ideas.
Within only a few years almost every manufacturer had adopted the same techniques, which would continue to be used for many decades to follow. The method of EHT generation was not however without its difficulties due to the extreme transformer insulation requirements of the EHT winding of the line output transformer. Indeed, at the start of the 50's some set manufacturers were producing as many as three times as many line output transformers as they did television sets !
In an interesting twist, the basic circuit given in the 1932 patent was not to be implemented as-is until the development of transistorised line-output stages in the 1960's.
Valves and C.R.T.s
The start of the year sees the introduction of very high voltage metal recifiers suitable for use as E.H.T. rectifiers. Presumably they must have been quite expensive since I can't find any television in the following 15 years that used anything other than a valve for EHT rectification.
In mid-August Mullard announce the introduction of two new C.R.T.s, the MW22/14C (9-inch) and MW31/14C. These could be used as direct replacements of the earlier MW22/7 and MW31/7 but could operate with a much reduced first anode voltage. Heater insulation was also much improved, allowing the new tubes to be connected in series heater chains. Two versions of each of these tubes was available, those without the 'C' having an additional conductive coating on the outside of the CRT. These three imporvements made these tubes ideal for sets using the new AC/DC chassis techniques, such as the Pye B18T.
A new test card, 'Test Card C', was introduced in March and was radiated from Alexandra Palace between 10am and 11am daily. This is arguable the first real test card in as much as its design encompesses just about every feature required for test purposes, including :-
The magazine "Wireless and Electrical Trader" had, since before the war, been including a radio service sheet with each copy of the magazine. In their 26th June edition they introduce their first sheet covering televisions, sheet #867, covering the HMV 1804/4 and Marconiphone VT50 models. Today such service sheets are a valuable resources for those interested in the repair of vintage televisions.
Pilot introduced their first television set, the distinctly
pre-war looking model VS9.
McMichael introduced their first post-war television, a combined TV and radiogram (pictured towards the top of this page).
In March Holland begin experimental transmissions from a Philips factory, covering an area of about 30 miles. However it would be another three years before the Netherlands government licensed the beginning of a regular service.
In April, Wireless World magazine gave details of the television service operating in Russia, basically that there were currently two transmitters (one in Moscow and one in Leningrad). Presumably Leningrad was radiating test transmissions since regular tranmissions there didn't start until August.
Also in April, France begins test transmissions of its new 819-line service from the Eiffel Tower, Paris, with a second transmitter to open later in the year at Lille. It was stated that the then current 455-line system which transmitted 21 hours per week would continue to be available until 1958 (although a rather convenient fire bought the system to a close several years early).
Canada builds it's first television transmitter at Montreal which was due to be opened in the Autumn.
In October, Pilot Radio Corporation of America introuced what was probably the first "personal television". Utilising a 3-inch C.R.T. it was to be known as the "Candid T-V" and cost $99.50 . Housed in an aluminium case te set weighed "only" 35Lb.
The Australian Government asked for tenders for the supply and erection of two 5kW television transmitters, one each for Sydney and Melbourne, with a closing date of November 25th. However nothing seems to have come of this as it was to be another seven years before television came to Australia.
At the very end of the year an American company began manufacture of a "all-metal" C.R.T. Most of the tube was made of spun chrome-steel alloy with a nearly flat plate glass for the face. The advantages claimed for this 16-inch tube were lighter weight, larger viewing area and better sheilding from ambient light. Similar tubes would be introduced later in the UK by English Electric and Mullard but not until the start of the 1950's. The same method was used by EMI to manufacture a 21-inch CRT in 1951, then the largest direct-view picture available in the UK.
|Gallery of Sets from 1948
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12th February 2005