Club hears insight on history of radio
Titanic tragedy features in fascinating talk
At the August meeting of the Kirkcudbright and District Probus Club the speaker was Terry Hughes talking about the history of radio.
The first person to predict the existence of radio waves was the gifted mathematician James Clerk Maxwell who lived in Parton.
He took equations published by Ampere in 1823 and Faraday’s rule published in 1831 which looked at the relationships between magnetism and electricity and used some fancy mathematics developed by Issac Newton in the 17th century to show that light and sound were transmitted in waves like waves in the sea.
Maxwell never demonstrated that radio waves existed. It was left to Heinrich Hertz, a German physicist to prove the existence of electromagnetic waves.
Hertz demonstrated that an electrical spark produced on one side of his laboratory could be detected on the other side of the laboratory. He did not realise the full potential of his discovery and it was Gugliemo Marconi who developed it and sent a radio signal from Cornwall to Newfoundland 1896, the first transatlantic broadcast.
He realised the importance of radio for communication with ships and set up a company to manufacture radios and to train radio operators.
Radio played a great part in the story of the sinking of the Titanic. The two radio operators stayed at their post sending out distress signals till the ship went down.
Unfortunately the closest vessel had switched off her radio and the operator had gone to bed so it was the Carpathia, 30 miles away that received the signal.
The findings of the inquiry into the disaster resulted in all ships being required to carry radios which had to be manned 24 hours a day.
The early radios transmitted over a wide range of frequencies resulting in interference between transmissions.
The problem was solved by the invention of the thermionic valve by Ambrose Fleming which allowed radios to transmit on a single frequency.
Valves have now been almost totally replaced by transistors invented by William Shockley. Transistors greatly reduced the size of equipment and increased their power and reliability.
The International Telecommunications Union, set up in 1927, regulates the use of the radio wavebands. The long wave band was used by radio stations but needs very large aerial arrays so has generally fallen out of use.
The medium wave is used by a large number of radio stations. The short wave has a very short range and was not thought to be useful so the ITU gave it all to radio amateurs.
But the radio amateurs found that they could bounce the radio waves off the ionosphere to arrive back on earth 1,000 miles or more away. It suddenly had commercial value and ITU took all but four frequencies back.
However, most radio stations allocated short wave were used for government propaganda and very few people listened. So the ITU gave more bands back to the amateurs.
Television used the very high frequency ( VHF) band but has mostly moved to ultra high frequency (UHF).
VHF is now mainly used by ship to shore and aeronautical communication, taxies and police. The UHF is used by TV and mobile phones and Super High Frequency by radar and space transmissions.
Terry then spoke about his enthusiasm for amateur radio and the qualifications he needed to be allowed to broadcast.
He concluded with a brief discussion about the early days of television, invented by John Logie Baird, and the importance of radar to the Battle of Britain, invented by Watson Watt.