Charles Samuel Franklin
Encyclopedia
Charles Samuel Franklin who published as C. S. Franklin, was a noted British
radio pioneer.
Franklin was born in London
, the youngest of a family of 13, and educated at Finsbury Technical College in Finsbury
, England
, under Silvanus P. Thompson
. After graduation in 1899 he joined the Marconi Company
where he spent his entire professional career. He was first sent to South Africa
to provide equipment for the Boer War
, then spent 2 years in Russia
. After his return to the UK, he invented a number of important radio devices including the variable capacitor
(patented 1902), ganged tuning (1907), variable coupling (1907), coaxial cable
, and the Franklin oscillator.
Today Franklin is best known for the Franklin beam aerial, his shortwave
antenna
. From the Marconi company's Poldhu
station in 1923 and 1924, he sent shortwave transmissions to Guglielmo Marconi
on his yacht Electra in the South Atlantic.
He received British patent 242342 in 1924 for "a pronounced directional effect from aerials of the type that are electrically long in comparison with the signal wavelength".
Alas, this antenna is so physically tall (about 1,813 feet at 540 kHz, and about 612 feet at 1600 kHz) that its use is generally restricted to frequencies of 1460 kHz and above with one example at 1500 kHz (KSTP, St. Paul, MN, non-directional, daytime only) and two examples at 1530 KHz (KFBK, Sacramento, CA, directional day and night using different parameters day and night).
Pseudo-Franklins have been employed below 1500 kHz, however, to good effect, but no where near as good as a true Franklin.
A true Franklin (180 over 180 degrees; 360 degrees, total) has an efficiency of about 510 mv/m/kW at 1 km. A pseudo-Franklin (180 over 120 degrees; 300 degrees, total) has an efficiency of about 470 mv/m/kW at 1 km. Another pseudo-Franklin (120 over 120 degrees; 240 degrees, total) has an efficiency of about 430 mv/m/kW at 1 km.
As a conventional antenna of 225 degrees has an efficiency of about 440 mv/m/kW at 1 km, exceeding that of a 120 over 120 degree pseudo-Franklin, one might naturally assume that a 225 degree antenna would be preferred, but this is not the case for powers above about 5 kW as a self-cancellation effect occurs in the fringe reception area.
For 10 kW and above, 195 degrees is optimum (about 400 mv/m/kW at 1 km), or a pseudo-Franklin or a Franklin may be employed, where each of these avoids or significantly reduces this self-cancellation.
Franklin was also active in early television
development. In 1935 the trustees leased part of Alexandra Palace
to the BBC
, which used it as the production and transmission center for their new BBC Television Service
. Franklin designed its antenna, and the world's first public broadcasts of high-definition television
were made from this site in 1936.
Franklin received the 1922 IRE Morris N. Liebmann Memorial Award
"for his investigations of short wave directional transmission and reception".
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
radio pioneer.
Franklin was born in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, the youngest of a family of 13, and educated at Finsbury Technical College in Finsbury
Finsbury
Finsbury is a district of central London, England. It lies immediately north of the City of London and Clerkenwell, west of Shoreditch, and south of Islington and City Road. It is in the south of the London Borough of Islington. The Finsbury Estate is in the western part of the district...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, under Silvanus P. Thompson
Silvanus P. Thompson
Silvanus Phillips Thompson FRS was a professor of physics at the City and Guilds Technical College in Finsbury, England. He was elected to the Royal Society in 1891 and was known for his work as an electrical engineer and as an author...
. After graduation in 1899 he joined the Marconi Company
Marconi Company
The Marconi Company Ltd. was founded by Guglielmo Marconi in 1897 as The Wireless Telegraph & Signal Company...
where he spent his entire professional career. He was first sent to South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
to provide equipment for the Boer War
Boer War
The Boer Wars were two wars fought between the British Empire and the two independent Boer republics, the Oranje Vrijstaat and the Republiek van Transvaal ....
, then spent 2 years in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. After his return to the UK, he invented a number of important radio devices including the variable capacitor
Variable capacitor
A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C circuits to set the resonance frequency, e.g. to tune a radio , or as a variable reactance, e.g...
(patented 1902), ganged tuning (1907), variable coupling (1907), coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
, and the Franklin oscillator.
Today Franklin is best known for the Franklin beam aerial, his shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
. From the Marconi company's Poldhu
Poldhu
Poldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula; it comprises Poldhu Point and Poldhu Cove. It lies on the coast west of Goonhilly Downs, with Mullion to the south and Porthleven to the north...
station in 1923 and 1924, he sent shortwave transmissions to Guglielmo Marconi
Guglielmo Marconi
Guglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...
on his yacht Electra in the South Atlantic.
He received British patent 242342 in 1924 for "a pronounced directional effect from aerials of the type that are electrically long in comparison with the signal wavelength".
Alas, this antenna is so physically tall (about 1,813 feet at 540 kHz, and about 612 feet at 1600 kHz) that its use is generally restricted to frequencies of 1460 kHz and above with one example at 1500 kHz (KSTP, St. Paul, MN, non-directional, daytime only) and two examples at 1530 KHz (KFBK, Sacramento, CA, directional day and night using different parameters day and night).
Pseudo-Franklins have been employed below 1500 kHz, however, to good effect, but no where near as good as a true Franklin.
A true Franklin (180 over 180 degrees; 360 degrees, total) has an efficiency of about 510 mv/m/kW at 1 km. A pseudo-Franklin (180 over 120 degrees; 300 degrees, total) has an efficiency of about 470 mv/m/kW at 1 km. Another pseudo-Franklin (120 over 120 degrees; 240 degrees, total) has an efficiency of about 430 mv/m/kW at 1 km.
As a conventional antenna of 225 degrees has an efficiency of about 440 mv/m/kW at 1 km, exceeding that of a 120 over 120 degree pseudo-Franklin, one might naturally assume that a 225 degree antenna would be preferred, but this is not the case for powers above about 5 kW as a self-cancellation effect occurs in the fringe reception area.
For 10 kW and above, 195 degrees is optimum (about 400 mv/m/kW at 1 km), or a pseudo-Franklin or a Franklin may be employed, where each of these avoids or significantly reduces this self-cancellation.
Franklin was also active in early television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
development. In 1935 the trustees leased part of Alexandra Palace
Alexandra Palace
Alexandra Palace is a building in North London, England. It stands in Alexandra Park, in an area between Hornsey, Muswell Hill and Wood Green...
to the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
, which used it as the production and transmission center for their new BBC Television Service
BBC One
BBC One is the flagship television channel of the British Broadcasting Corporation in the United Kingdom. It was launched on 2 November 1936 as the BBC Television Service, and was the world's first regular television service with a high level of image resolution...
. Franklin designed its antenna, and the world's first public broadcasts of high-definition television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
were made from this site in 1936.
Franklin received the 1922 IRE Morris N. Liebmann Memorial Award
IEEE Morris N. Liebmann Memorial Award
The initially called Morris Liebmann Memorial Prize provided by the Institute of Radio Engineers , the IEEE Morris N. Liebmann Memorial Award was created in 1919 in honor of Colonel Morris N. Liebmann. It was initially given to awardees who had "made public during the recent past an important...
"for his investigations of short wave directional transmission and reception".
Additional References
- K. G. Beauchamp, History of Telegraphy, IET, 2001, page 234. ISBN 0852967926.
- W. J. Baker, History of the Marconi Company 1874-1965, Routledge, 1996, Page 280. ISBN 0415146240.
- Oxford Dictionary of National Biography
- Radio Marconi memorial (Patent 242342)