68P80801E30-A 5/1/2002 6-31
Gen 3 Site Controller System Manual Chapter 6 System Testing
Site Reference
Site Reference
The site reference outputs provide a timing reference and a frequency
reference to the base radios. The timing reference is one pulse per second
(1PPS) derived from the GPS receiver. The frequency reference is a 5 MHz
signal from a high stability oscillator. In addition, the high stability oscillator
is trained to GPS to eliminate aging and temperature effects.
The site reference signal is a combined 1PPS/5MHz signal. It is combined
by altering the duty cycle of the 5MHz frequency reference such that the
change from a 25% to 75% duty cycle represents the 1PPS timing mark. In
order for the base radios to properly decode the 1PPS/5MHz signal, it must
meet the mask shown below in Figure 6-3 at the input of each base radio.
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