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Appendix VII

Author: Edmund A. Laport

Minimum Operating Signal-to-noise Ratios for Various Classes of Commercial Service in Telecommunication

Type of Radio Service Approximate Minimum S/N (Decibels)
Double-sideband radiotelephony (3-kilocycle bandwidth) 15
Single-sideband radiotelephony (3-kilocycle bandwidth) 9
Broadcasting (5-kilocycle bandwidth) 26
Manual Morse radiotelegraphy (for average operators) 0
Frequency-shift radiotelegraphy (60-word teleprinter speed) 6
Single-sideband two-tone radiotelegraphy, one tone marking and one tone spacing, 60-word speed 8
Single-sideband four-tone radiotelegraphy, two tones marking and two tones spacing, 60-word speed 6
Radio facsimile with 8-decibel contrast ratio using double-sideband amplitude modulation 18
Radio facsimile with 8-decibel contrast ratio using carrier-shift 12

NOTE 1: The signal-to-noise ratios given are those required for reliable commercial operation, assuming the limiting factor is only noise. NOTE 2: Noise includes all extraneous interference due to atmospheric static, man-made static, or interfering signals from other stations.

NOTE 3: Professional operators engaged in handling telegraph or telephone traffic often are able to copy faithfully when S/N is 10 to 15 decibels below the values stated for 1, 2, and 4. The others, with the exception of 3, are intrinsically machine methods.

NOTE 4: Consult documents of the International Radio Consulting Committee (CCIR) for standards under study on this subject.

Last Update: 2011-03-20