Repeaters for Law Enforcement Communication Systems-Law Enforcement Standards Program,

摘要

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.