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1887

Journal of the Institution of Electronic and Radio Engineers

Volume 57, Issue 5, September October 1987

Volumes & issues:

Volume 57, Issue 5

September October 1987

Instabilities in dual stepping motor systems
A precise, automated test system for video tape noise evaluation
  • Author(s): S.P. Johnson
  • Source: Journal of the Institution of Electronic and Radio Engineers, Volume 57, Issue 5, p. 207 –212
  • DOI:  10.1049/jiere.1987.0071
  • Type: Article
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  • p. 207 –212 (6)
    An automated test system for tape noise evaluation in colour-under type video systems is described. The system, which is currently used for VHS media testing, allows thorough high-precision electromagnetic performance evaluation by non-technical personnel. An analysis of luminance and chrominance output and noise characteristics for a sample is completed in less than four minutes. A high-precision capability is included to perform digital trace averaging over a number of spectral measurements. The high-precision mode of operation allows measurement of luminance and chrominance output with a standard deviation of 0.2 dB and luminance and chrominance noise with a standard deviation of 0.5 dB. Digital storage of spectrum traces enables compensation for system noise to be made over a broad spectral range instead of a single frequency, and a numerical integration of the noise power in the signal channel is easily accomplished. Results presented show how the high precision of the measurement technique may be used to determine the rate of head accommodation to a particular tape.
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A review of the design of helical resonator filters
  • Author(s): N.P. Spencer
  • Source: Journal of the Institution of Electronic and Radio Engineers, Volume 57, Issue 5, p. 213 –220
  • DOI:  10.1049/jiere.1987.0072
  • Type: Article
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  • p. 213 –220 (8)
    The design procedure for helical resonator filters, the attempts to model the resonator and the derivation of the design equations are briefly reviewed. Also presented are a series of measurements that were made to assess the accuracy of the design equations, with a view to developing a computer-based design facility. The work has shown that the design equations do not allow a resonator to be designed in a single step, i.e. the dimensions require adjusting by measurement. A resonator made to the dimensions predicted by the equations will always require shortening to obtain the correct resonance. In addition to predicting the resonator dimensions, it is necessary to relate the inter-resonator aperture to the required coupling coefficient. The variation of coupling coefficient with aperture size has been measured and a series of curves are presented. Using the measured data in the form of look-up tables, design software has been developed that enables a one-step filter design to be performed.
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A 580 kHz switching regulator using on-off control
A 500 m experimental range for propagation studies at millimetre, infrared and optical wavelengths
  • Author(s): C.J. Gibbins ; D.G. Carter ; P.A. Eggett ; K.A. Lidiard ; M.G. Pike ; M.A. Tracey ; E.H. White ; J.M. Woodroffe ; U.M. Yilmaz
  • Source: Journal of the Institution of Electronic and Radio Engineers, Volume 57, Issue 5, p. 227 –234
  • DOI:  10.1049/jiere.1987.0074
  • Type: Article
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  • p. 227 –234 (8)
    A 500 m experimental range which has been constructed to carry out propagation studies at millimetre, infra-red and optical wavelengths is described. The range is a well- instrumented open-air laboratory where the transmissions are monitored simultaneously with a comprehensive set of meteorological measurements to obtain propagation data required to develop prediction models of use in the design of future communications systems. Some examples are given of studies of attenuation in rain, snow and fog, and of the effects of scintillation.
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High density data storage on audio compact cassette tape using a low-cost tape transport
  • Author(s): T. Donnelly ; D.J. Mapps ; R. Wilson
  • Source: Journal of the Institution of Electronic and Radio Engineers, Volume 57, Issue 5, p. 235 –238
  • DOI:  10.1049/jiere.1987.0075
  • Type: Article
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  • p. 235 –238 (4)
    A parallel encode/decode software algorithm has been designed for the recently developed ISS 2/3 code. In addition a low-cost solution has been applied to the problem of tape—head azimuth variation (tape skew). The above enables the recording and playback of direct digital data at 60 kb/s on normal audio compact cassette tape using an 8-track format.The combination of a low-cost tape transport and a standard audio cassette tape produces a high degree of tape skew. This is overcome by encoding control pulses on the outer tracks which are used to introduce the same amount of data skew into the clock signals used to clock the data off the tracks. The self-clocking ISS 2/3 code facilitates clock regeneration which, together with simple de-skew circuitry and software encoding/decoding permits the realization of a low-cost bulk storage system. An increase in the data rate to 1 00 kb/s is possible through the use of equalization and by incorporating data onto the outer, de-skew tracks.
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Book review: Nonlinear Circuits

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