Charles Samuel Franklin (23 March 1879 – 10 December 1964), who published as C. S. Franklin, was a noted

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radio pioneer.

Biography

Franklin was born in

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, the youngest of a family of 13, and educated at Finsbury Technical College in

Finsbury Finsbury is a district of Central London, forming the southeastern part of the London Borough of Islington. It borders the City of London. The Manorialism, Manor of Finsbury is first recorded as ''Vinisbir'' (1231) and means "manor of a man c ...

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, under Silvanus P. Thompson. After graduation in 1899 he joined the

Marconi Company The Marconi Company was a British telecommunications and engineering company founded by Italian inventor Guglielmo Marconi in 1897 which was a pioneer of wireless long distance communication and mass media broadcasting, eventually becoming on ...

where he spent his entire professional career. He was first sent to

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to provide equipment for the

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, then spent 2 years in

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. 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 Coaxial cable, or coax (pronounced ), is a type of electrical cable consisting of an inner Electrical conductor, conductor surrounded by a concentric conducting Electromagnetic shielding, shield, with the two separated by a dielectric (Insulat ...

, and the Franklin oscillator. Today Franklin is best known for the Franklin beam aerial, his

shortwave Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...

antenna. From the Marconi company's

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station in 1923 and 1924, he sent shortwave transmissions to

Guglielmo Marconi Guglielmo Giovanni Maria Marconi, 1st Marquess of Marconi ( ; ; 25 April 1874 – 20 July 1937) was an Italian electrical engineer, inventor, and politician known for his creation of a practical radio wave-based Wireless telegraphy, wireless tel ...

on his yacht Electra in the

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. Franklin was also active in early

television Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...

development. In 1935 the trustees leased part of

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to the

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, which used it as the production and transmission center for their new

BBC Television Service BBC One is a British free-to-air public broadcast television channel owned and operated by the BBC. It is the corporation's oldest and Flagship (broadcasting), flagship channel, and is known for broadcasting mainstream programming, which includ ...

. Franklin designed its antenna, and the world's first public broadcasts of high-definition

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". He died at Buckhurst Hill, aged 85.

High-efficiency medium-wave transmitting antenna

Franklin 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". (Patent 242342) The 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 1400 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 1400 kHz, however, to good effect, but nowhere 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.

"Rio" Treaty and other considerations

In some cases, a station's efficiency may be restricted to 362.10 mV/m/kW at 1 km for Class A stations, to 281.63 mV/m/kW at 1 km for Class B stations or to 241.40 mV/m/kW at 1 km for Class C stations, unless a higher efficiency was "grandfathered". If so restricted, then a high-efficiency antenna, such as a Franklin, could be employed only if the transmitter power was reduced accordingly. Older, "legacy" stations are more likely to be so "grandfathered" rather than newer, post-"Rio" stations, hence older, "legacy" stations are more likely to employ Franklin, pseudo-Franklin or other high-efficiency transmitting antennas. For practical reasons, 90 degrees (about 310 mV/m/kW at 1 km) is taken to be the "gold standard", but shorter (particularly for lower frequency stations) or taller (particularly for higher frequency stations) are often found. Also, for practical reasons, 199 feet antennas, occasionally with "top loading", are often specified as this is the maximum height in order to avoid tower lighting, and in a number of cases tower painting, for aviation obstruction purposes.

Footnotes

References

* K. G. Beauchamp, History of Telegraphy, IET, 2001, page 234. . * W. J. Baker, History of the Marconi Company 1874-1965, Routledge, 1996, Page 280. .
Oxford Dictionary of National Biography
* * (Patent 242342)
Patent 242342
{{DEFAULTSORT:Franklin, Charles Samuel Radio pioneers 1879 births 1964 deaths