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The programme looks at some fundamental concepts found in modern communications equipment such as frequency, waveforms, bandwidth and spectrum. These basic terms are explained and demonstrated usin...g a range of equipment including an oscilloscope and a Moog Synthesiser.
Metadata describing this Open University video programme
Module code and title: T101, Living with technology: a foundation course
Item code: T101; 06; 1980
First transmission date: 20-04-1981
Published: 1980
Rights Statement:
Restrictions on use:
Duration: 00:24:00
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Producer: Philip Ashby
Contributors: David Crecraft; John Naughton
Publisher: BBC Open University
Keyword(s): Communications; Spectrum; Waveforms
Footage description: John Naughton introduces the programme. Shots of Derek Grossmith playing a wind instrument. The sounds are displayed as waveforms as he plays. David Crecraft demonstrates the use of an oscilloscope. A strain gauge is attached to a ruler and then connected to the oscilloscope. Bending of the ruler is then seen as a moving spot on the oscilloscope screen. Crecraft goes on to adjust the oscilloscope to add a time base to the measurement. The spot on the screen now forms a wave. Crecraft freezes the picture so that the waveform can be seen more easily. He uses this wave to explain the concept of frequency. Using a Moog Synthesiser which is connected to an oscilloscope, Crecraft examines the waveform frequency of a variety of notes. He points out that the fundamental note is a pure sinusoid. Crecraft next analyses the notes played on the synthesiser with a machine which shows amplitude frequency spectrums. He also shows the spectrum for several instruments played by Derek Grossmith. From this he explains the difference between fundamentals and harmonics. Crecraft goes on to add several sine waves together to demonstrate that by adding sine waves, any sound can, in theory be created. Going back to the Moog Synthesiser, Crecraft demonstrates that harmonics are always multiples of the fundamental frequency. Crecraft distinguishes between periodic and nonperiodic signals and explains why he uses periodic signals for his demonstrations. He goes on to explain the concept of bandwidth of a signal. The problem of noise in electronic signals is discussed and Crecraft explains how some of the problems of noise can be overcome by sending digital rather than analogue signals. He explains the difference between these two types of signal and also how a digital signal is obtained. Finally Crecraft explains the difference between amplitude and frequency modulation for communication is signals.
Master spool number: OU3268
Production number: FOUT039N
Videofinder number: 2192
Available to public: no