SECTION 3: DESCRIPTION AND STATION BLOCK DIAGRAM
Power Amplifier Module
The Power Amplifier Module takes the modulated rf paging signal and amplifies it in preparation for transmission. Finally, the paging signal is sent out over-the-air via an external transmit antenna.
The circulator provides 20 dB isolation between the power amplifier circuitry and the transmit antenna system. The circulator junction allows forward rf energy to pass through to the output, while routing any reflected rf energy to the 50-ohm load. If the heat sink temperature exceeds a preset threshold, the power amplifier will reduce output. If over-temperature persists, it will shut down completely. The harmonic filter reduces circulator harmonics. For improved isolation, there are circulator options available to add one or two circulators to the station.
An internal wattmeter allows front panel metering of rf power and VSWR.
The available Power Amplifier Modules are shown in the following table, along with the corresponding Exciter Mod¬ules and the resulting transmit frequency ranges.