Accession Number : AD0678552

Title :   ANALYSIS OF STRUCTURAL RETURN LOSS IN CATV COAXIAL CABLES,

Corporate Author : GENERAL CABLE CORP BAYONNE N J

Personal Author(s) : Lubars,H. ; Olszewski,J. A.

Report Date : DEC 1968

Pagination or Media Count : 27

Abstract : The analysis of structural return loss in CATV coaxial cables leads to the following conclusions: (1) SRL spikes (resonances) occur when the period length is equal to a half wavelength and integral multiplies of half wavelengths. (2) Maximum SRL spikes occur when the period is symmetrical. (3) The SRL spike due to the fundamental frequency can be of a lesser amplitude than spikes caused by the harmonic frequencies depending upon the asymmetry of the irregularity period. (4) The length of cable that can be effectively measured varies inversely with cable attenuation. It follows, therefore, that periodic impedance changes are more critical in low attenuation cables. (5) For a specific SRL value, the recent extension of requirements from 216 MHz to 300 MHz adds to the difficulty of meeting the requirement. (6) The recommended procedure for testing SRL is to match the cable average impedance by employing a variable bridge and termination. When a fixed 75 ohm bridge is used to measure cable whose impedance differs from 75 ohms, the voltage due to the mismatch may vectorially add to or subtract from the reflected voltage. By cutting a small length from the cable, the phase relationship of the unbalance voltage and reflected voltage may subtract to provide a better SRL reading. (Author)

Descriptors :   (*COAXIAL CABLES, *TELEVISION SYSTEMS), (*WAVE PROPAGATION, COAXIAL CABLES), STRUCTURAL PROPERTIES, REFLECTION, RESONANCE, ATTENUATION, ELECTRICAL IMPEDANCE

Subject Categories : Electrical and Electronic Equipment
      Radiofrequency Wave Propagation
      Non-radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE