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17-8.
For DSBSC generation the modulation audio is applied to the IF port of the input mixer through an
isolation network. With the output of the wideband amplifier switched to the local oscillator port, a DSBSC
1
signal is present at the RF port. Switching the Step Attenuator to the RF output port makes the DSBSC signal
available at the RF output.
17-9. Duplex Generator. The Duplex Generator output is a frequency component that is offset from the
system monitor frequency by 0 to 10 MHz or by 45 MHz. The offset is obtained by mixing the -20dBm local
oscillator signal from the wideband amp, which is already offset by 10.7 MHz, with a signal frequency from 10.7
MHz to 0.7 MHz or 34.3 MHz.
17-10.
For the 34.3 MHz mixing signal, a single VCO is used. Tuning of the VCO is with the OFFSET FINE
TUNE line from the front panel. Frequency modulation of the VCO is implemented by suming the OFFSET
MOD signal with the tuning voltage.
17-11.
For the 0.7 MHz to 10.7 MHz mixing signal a VCO with a frequency range from 35 MHz to 45 MHz is
mixed with the 34.3 MHz VCO. The 35-45 MHz VCO is tuned by the OFFSET COARSE TUNE line from the front
panel.
17-12.
A sample ofthe offset frequency is made available to the frequency counter on the OFFSET FREQ line.
The processor uses the frequency information to calculate and display the actual duplex frequency.
17-2
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