Monitor Mode Block Diagram - Motorola R-2001A Service Manual

5-44. The 10.7 MHz difference signal at the IF port of the receive mixer is amplified and selected by the first IF
Amplifier and Filter. The Amplifier provides sufficient gain so that the overall gain of the RF Input module is 10
±2 dB. The I F filter provides a modulation acceptance bandwidth of +100 kHz. The filter output is the 10.7 MHz
IF signal to the Receiver module (A4).
5-45. A second mixer in the receiver module down converts the 10.7MHz IF signal to 455 kHz by mixing the
input signal with a 10.245 MHz Second Local Oscillator. The Second Local Oscillator is phase locked to the 10
MHz system standard so that its frequency is as accurate as the standard. The phase locked loop for the
Second Local Oscillator is split between two modules. A 10.245 MHz SAMPLE signal is compared with the
REFERENCE FREQUENCIES from the RF Synthesizer on the Processor I/O module (A7). The comparison
provides a TRACKI NG VOLTAGE error signal to the 10.245 MHz oscillator which corrects its frequency to hold
it in lock.
5-46. Immediately following the second mixer is the IF filter. The IFfilter is selectable between a narrowband
(±6 kHz mod acceptance) and a wideband (±100 kHz mod acceptance) bandwidth. The bandwidth is under the
control of the processor and is selected by the bandwidth switch on the front panel.
Figure 5-6. Monitor Mode Block Diagram
5-13