Published Resources Details
Journal Article
- Title
- An experimental Frequency-Modulated broadcast transmitter
- In
- Journal of the Institution of Engineers, Australia
- Imprint
- vol. 20, no. 9, Sep 1948, pp. 107-117
- Description
This paper, No. 964, originated in the Sydney Division of The Institution, and was presented before a General Meeting of the Electrical and Communication Engineering
Branch of the Division, on 22nd October, 1947.The authors are on the staff of the Research Laboratories, Amalgamated Wireless (Australasia) Ltd.
[This paper was awarded the Electrical Association Premium 1947.]
- Abstract
A description is given of a 250-watt f.m. broadcast transmitter which complies with the requirements of the American Federal Communications Commission "Standards of Good Engineering Practice Concerning F.M. Broadcast Stations." The equipment described includes the frequency-modulator unit, power-amplifier unit, aerial array, and station monitor. The frequency modulator depends for its operation upon the time delay which occurs when a f.m. signal is passed through a multi-section band-pass filter. A signal from a fixed-frequency source is mixed with an f.m. signal from a reactance-valve modulated oscillator; the f.m. difference-frequency component is selected, and after passage through a time-delay
network, is once more mixed with the original f.m. signal.
The difference-frequency component in the output of this second mixing stage has the same centre frequency as the fixed source and is phase modulated; pure frequency modulation is obtained if the audio input is passed through an inverse-frequency network before application to the modulator. In an experimental unit, a maximum phase-angle deviation of approximately ± 5 radians is obtained at a fundamental frequency in the vicinity of 300 kc.; a frequency multiplication of 324 times yields an output in the 88 to 108 Mc. band with a deviation of ± 75 kc.
Related entries
Corporate Bodies
People
See also
Related Published resources
isRelated
- 'Electrical Association Premium - 1947 Award', Journal of the Institution of Engineers, Australia, 21 (6) (1949), 104. Details