REPEATERS FOR LAW ENFORCEMENT COMMUNICATION SYSTEMS LAW ENFORCEMENT STANDARDS PROGRAM

• NCJ Number: 14521
• Author(s): R M JICKLING; J F SHAFER
• Date Published: 1974
• Length: 23 pages
• Sponsoring Agency: US Dept of Justice; US Dept of Justice NIJ Pub
• Corporate Author: US Dept of Justice
• Sale Source: Superintendent of Documents, GPO; National Technical Information Service; National Institute of Justice/
• Language: English
• Country: United States of America
• Note: NATIONAL INSTITUTE OF LAW ENFORCEMENT AND CRIMINAL JUSTICE STANDARD PREPARED BY NATIONAL BUREAU STANDARDS

Annotation

DISCUSSION OF DEVICES USED IN LAND MOBILE COMMUNICATIONS SYSTEMS, WHICH RECEIVE, AMPLIFY, AND RETRANSMIT SIGNALS TO PROVIDE IMPROVED COMMUNICATION RANGE AND COVERAGE.

Abstract

EVEN WITH A GOOD BASE STATION ANTENNA SITE, IT IS POSSIBLE THAT A HILL, A BUILDING, OR OTHER OBSTRUCTION CAN CAUSE A SHADOW REGION WHERE RECEIVED SIGNALS ARE EXTREMELY WEAK. IN SUCH CASES, RATHER THAN ATTEMPTING TO IMPROVE SIGNAL STRENGTH BY INCREASING THE POWER RADIATED BY THE BASE STATION, AN UNMANNED REPEATER STATION CAN BE LOCATED OUTSIDE THE SHADOW REGION TO RETRANSMIT RECEIVED SIGNALS INTO THE REGION AND VICE VERSA. IN ITS SIMPLEST FORM, A REPEATER CONSISTS OF A RECEIVER ON ONE FREQUENCY WITH ITS AUDIO OUTPUT CONNECTED TO THE AUDIO INPUT OF A TRANSMITTER OPERATING ON A SECOND FREQUENCY. USE OF REPEATERS ENHANCES MOBILE-TO-MOBILE COVERAGE IN TERRAIN THAT WOULD OTHERWISE RESULT IN UNSATISFACTORY COMMUNICATIONS. PERSONAL TRANSCEIVERS, WITH THEIR LOW POWER AND REDUCED ANTENNA EFFICIENCY, ALSO BENEFIT FROM THE INCREASED SIGNAL STRENGTH PROVIDED BY THE REPEATER. THIS REPORT IS CONCERNED WITH FM REPEATERS USED IN LAND MOBILE COMMUNICATIONS SYSTEMS. REPEATER SYSTEMS ARE DESCRIBED WITH EMPHASIS ON APPROPRIATE ANTENNA SITE SELECTION, SIGNAL-REJECTION TECHNIQUES, AND SPECIALIZED TRANSMISSION-LINE COMPONENTS FOR THE TRANSMISSION AND RECEPTION OF SIGNALS. REPEATERS USING THE VEHICLE TRANSCEIVER ARE MENTIONED. REPEATERS AT MICROWAVE FREQUENCIES ARE DESCRIBED TO THE EXTENT THAT THEIR USE FOR CONTROL AND AS AUDIO LINKS IS PERTINENT. MEASUREMENT TECHNIQUES THAT ARE UNIQUE TO LAND-MOBILE REPEATERS ARE DISCUSSED. SPECIALIZED ANCILLARY EQUIPMENT NECESSARY FOR THE EFFICIENT FUNCTIONING OF REPEATER SYSTEMS IS BRIEFLY DESCRIBED AND A GLOSSARY OF TECHNICAL TERMS IS PROVIDED. (SNI ABSTRACT)