The Valve Era

An Early Fleming Valve.

Like many other wars, the first world war speeded up the development of technology that was useful for the war effort. Although Sir Ambrose Fleming invented the valve rectifier in 1904, and Lee de Forest invented the triode in 1905, the inability to produce a good vacuum meant that these devices were unreliable and had a short life. In 1913, Irving Langmuir, who was an American scientist developed a method of producing an excellent vacuum. French military scientists quickly used his technique to produce a reliable and efficient triode valve, which was called the 'R' valve. It was used in military communication equipment and was produced in large numbers. After 1916 the valve was also produced in England by Osram, BTH and Ediswan who were all lamp manufacturers.

When the war ended, large numbers of these valves appeared on the surplus market and so were readily available. Many people were interested in the new technology, began building receivers and the number of radio amateurs grew rapidly.  The new valves made it possible to easily transmit high quality speech and music, and allowed high sensitivity receivers to be developed. 

People quickly realised the potential for the commercial broadcasting of speech and music, and the Marconi Company began test transmissions on 2,750 metres, from Chelmsford, early in 1920. Some of the transmissions consisted of readings from Bradshaw's railway timetable, others included gramophone records and recitals by local musicians. Many radio amateurs and ship's radio operators tuned in to the transmissions. This greatly encouraged Marconi and on 15th June a 30 minute recital was given Dame Nellie Melba. The transmission was sponsored by the Daily Mail and was given a lot of coverage in the press. It was also received all over Europe. Many other transmissions of music were made throughout the summer. Transmissions continued until the autumn, when the Post Office stopped issuing the authorisation that was required for each transmission. This was because of complaints of interference with military communications.
A Bullen 'Bullphone Nightingale' loudspeaker from 1926.

An Amplion 'Swan-neck' De Luxe loudspeaker from 1926.
Receivers in those days were extremely unselective and speech and music required a comparatively large space on the long wave band. Luckily there was an alternative entertainment station that broadcasted speech and music. The Dutch PCGG station started broadcasting in April 1920. Each week concerts were transmitted on Sunday afternoons, and Monday and Thursday evenings. Announcements were made in Dutch, French and English. The first complete wireless receivers appeared in the UK in 1920. They were made by the British Thomson Houston Company (BTH). Others introduced in 1921, were manufactured by Burnham & Company, who later became Burndept, and L. McMichael Limited. In the USA commercial broadcasting was a great success. There was a big demand for receivers, and by 1922 many stations were broadcasting. This fuelled interest in this country, and manufacturers eagerly wanted to echo the success of their American counterparts.
The Post Office came under pressure to allow national broadcasting. By the end of May 1922 it had received 23 applications to start broadcasting, and something had to be done. On 18th May the Post Office met representatives from 18 companies and asked them to come up with a cooperative scheme for broadcasting. Discussions went on for 5 months without any proposal. Each company had its own interests and there was much conflict. The government and the press complained at the delay and on 18th October proposals were finally put to the industry. The result was the setting up of the British Broadcasting Company, which would broadcast from eight transmitters, covering most of the larger areas of population. Capital was provided by the six largest companies: Marconi, GEC, BTH, Metropolitan Vickers, Western Electric and the Radio Communication Company.
A Hart wireless accumulator from 1926.

Any British manufacturer or retailer could become a member by purchasing at least one £1 share. Listeners would buy a 10 shilling receiving licence and would pay two tarriffs. The first was based upon the various components in the receiver and went to the BBC. The second was a levy of 12s.6d per valveholder which went to the Marconi Co. as a royalty.

The Technical Details of Valve Receivers


The 2LO aerials that were on the roof 
of Selfridges in Oxford Street, London.

On Tuesday 14th November 1922, the first BBC station 2LO started broadcasting in the Medium Waveband, from the roof of Selfridges in Oxford Street, London. The next day 5IT started broadcasting in Birmingham, and 2ZY went on the air in Manchester. 2LO reached an audience of about 18,000. By October all of the stations were in operation, and reached about half of the population, with signals that were strong enough to be received by a crystal set. In July 1925 the BBC opened a high power long wave transmitter at Daventry, which reached 55% of the population. 
By this time about 85% of the population could receive the transmissions. Although many different valve receivers were available from about 1923, crystal sets remained the most popular receivers for several years. This was due to their low cost and freedom from the expensive high tension batteries, and the re-charging of the low tension accumulators in the valve receivers. The early valves also had a relatively short life and so needed frequent replacement. Although crystal sets could only operate headphones, it was possible to connect several of them to a receiver so that a family could listen together. By the summer of 1925, one and a half million receiving licences had been issued.

In the 1920's and 30's there were large numbers of radio kits on the market. These were popular as they were a lot cheaper than the ready built receivers. The receiver on the right was built from a typical kit.

Valve receivers had the advantage of being able to operate a loudspeaker. Initially these were horn loudspeakers, but soon more modern types were developed which could be housed in the same cabinet as the receiver, to provide good sound quality. The early valve receivers were mostly of the tuned radio frequency (TRF) type, which often had an array of different knobs and switches on the front panel. Tuning-in a station required the operation of several controls, and to change waveband sometimes required the plugging-in of different tuning coils. Many receivers had a reaction control which adjusted the sensitivity and selectivity. If this was advanced too far, the receiver would burst into oscillation and act like a transmitter, so interfering with everyone else's receiver in the neighbourhood.
An early moving coil loudspeaker, which was similar to the modern version.

An early Cossor radio.

The modern type of receiver, which is called a super heterodyne, or superhet for short, appeared in 1925. This produced the highly sensitive and selective receiver, with few tuning controls, that we are used to today. Mains powered receivers and battery eliminators appeared in 1926. The first mains powered receiver to entirely dispense with batteries, was the 'Baby Grand', made by Gambrell Brothers Limited. In those days mains electricity was provided by hundreds of small companies which supplied electricity in a variety of different voltages, frequencies and even D.C. When the national grid was set up in the early 1930's, it standardised the supply and made it much easier to produce mains power supplies for receivers. It also helped to establish mains powered radios. At the end of the 1920's, the number of receiving licences had risen to three million.

By the 1930's valves had become very reliable and the price of receivers had started to fall. The first push button radios were produced in the mid 1930's, and short wave bands were popular, which gave the listener access to much of the world. Smaller valves were developed during the second world war, which eventually gave rise to the more compact receivers of the late 1940's and early 1950's. Most of the popular B.B.C. medium and long wave stations that we are familiar with today, were broadcasting by the late 1940's. The Light Programme (Radio 4) started broadcasting on 29th July 1945, on 1500 metres, in the long wave band.

 In the 1950's internal aerials became standard and small miniature battery operated valves were produced for the first truly portable receivers. In the early 1950's, the BBC began experimenting with  FM, VHF broadcasts, to offer high quality, interference and noise free reception. The first station officially opened on 2nd May 1955. The performance of some of the early FM receivers left a lot to be desired, especially in terms of the VHF circuitry and FM detection. But soon things improved and FM receivers became commonplace. In the late 1950's radiograms became popular, and catered for the rapidly growing interest in records.Valve radio development ended in the early 1960's as transistors began to take over.
A Vidor valve portable from 1954.


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