EXPERIMENTAL MEASUREMENT OF PATH NOISE IN ULTRA-NARROWBAND RADIO SYSTEMS (SYNCTRAN)

• NCJ Number: 43218
• Author(s): ANON
• Date Published: 1977
• Length: 62 pages
• Contract Number(s): J-LEAA-025-73
• Sponsoring Agency: US Dept of Justice NIJ Pub
• Corporate Author: US Dept of Justice; Aerospace Corporation
• Publication Format: Document
• Language: English
• Country: United States of America

Annotation

USE OF NARROW (ABOUT 30MHZ) RADIO BANDWIDTHS TO TRANSMIT ALARM SIGNALS THROUGH URBAN AND SUBURBAN NEIGHBORHOODS TO A CENTRAL SECURITY LOCATION WAS TESTED. NOISE INTERFERENCE COULD BE CONTROLLED.

Abstract

IN THIS SERIES OF EXPERIMENTS, 30MHZ BANDWIDTHS WERE USED TO TRANSMIT ALARM SIGNALS FROM TYPICAL URBAN AND SUBURBAN LOCATIONS TO A CENTRAL RECEIVER USING A LOCAL RADIO BROADCAST STATION SIGNAL AS A REFERENCE POINT FOR BOTH TRANSMITTERS AND RECEIVERS. THIS SYSTEM, CALLED 'SYNCTRAN', AN ACRONYM FOR 'SYNCHRONOUS TRANSMISSION,' WAS DEVELOPED TO OFFSET THE FACT THAT LOW-COST, READILY AVAILABLE NARROWBAND EQUIPMENT DRIFTS GREATLY AS THE RESULT OF TEMPERATURE VARIATIONS. IN THESE TESTS MAJOR SOURCES OF PATH NOISE WERE MOTOR VEHICLES, AIRCRAFT, AND VARIOUS UNIDENTIFIED PHENOMENA WHICH CREATED SIDEBAND NOISE. THIS INTERFERENCE COULD BE CONTROLLED BY TRANSMITTING IN SIDE BANDS LOCATED APPROXIMATELY 10 TO 50 HZ FROM THE CARRIER AND OPERATING AT FREQUENCIES IN THE 25-50 MHZ RANGE. WHILE LOW TRANSMITTER POWER MAY BE ADEQUATE IN MANY SYNCTRAN ALARM APPLICATIONS, A MORE RELIABLE SYSTEM COULD BE ACHIEVED IF THE TRANSMITTER HAD VARIABLE POWER OUTPUT OVER A RANGE OF 0.5 TO 5 WATTS. THIS WOULD INSURE A SIGNAL TO NOISE RATIO OF 30DB OR BETTER AND MINIMIZE LONG-TERM FADING. SYNCTRAN LINKS TO, FROM, OR BETWEEN MOBILE STATIONS ALSO APPEAR FEASIBLE.