Club hears in­sight on his­tory of ra­dio

Ti­tanic tragedy fea­tures in fas­ci­nat­ing talk

The Galloway News - - DISTRICT NEWS -

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.

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