The radio frequencies used by the ALERT network require a line of sight between the transmitter and receiver. The data transmission from a remote field station can be sent directly to the base station or, if this is not possible, the transmission can be relayed through a repeater station. A repeater located at a high topographic location can be used to achieve the line of sight necessary to successfully transmit a signal between radios.   The Orange County Alert System currently employs three repeaters.

Two Motorola repeaters on Santiago Peak receive data transmission on one of two frequencies and then retransmit the data on a different frequency to the base station receivers. The Santiago Peak repeaters receive data transmissions from all of Orange County and most of the Upper Santa Ana River watershed. One of the Santiago Peak repeaters operates on NWS licensed hydrologic radio frequencies and is used for rain gage, water level, and other weather data. The second Santiago Peak repeater operates on hydrologic frequencies licensed to Orange County and is used for pump station telemetry. It was necessary to install the second Santiago Peak repeater to handle pump station telemetry and remove the pump station transmission loading from the NWS frequency.

A Sierra-Misco smart repeater is located on the canyon rim above Laguna Beach. The Laguna Beach Repeater was needed in order to transmit data from the ALERT station in Laguna Canyon. The smart repeater receives data from within the canyon and then retransmits the data on the same frequency after a slight time lag.

Repeater Frequencies

System Components

ALERT System
Repeater Stations
Field Stations
Return Frequencies

Weather Forecasts
EMWIN System

Weather Imaging