General Dynamics C4 Systems URC-200 (V2)
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senses both forward and reflected power used by the ALC to determine the amount of attenuation
required by the VCA.
The transmitter is modulated with FM modulation only, using either Plain Text (audio) or Cipher
Text (data) signals. Both Plain Text and Cipher Text signals are processed through the same APPS
board filtering and amplification circuitry used to process baseband signals in the receive mode.
The APPS processor generates the 150 Hz tone (for transmit tone squelch), which is summed with
the FM PT transmit audio. The FM modulation signal is applied to the synthesizer where it is
superimposed on the Voltage Controlled Oscillator (VCO) control voltage. The VCO generates the
RF transmit signal and the frequency of the transmit signal is determined by the VCO control
voltage. By varying the VCO control voltage using the modulation signal, the VCO output
frequency varies directly in response to the modulation signal. This produces an FM modulated
transmit signal.
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