Crown FMX30 Manuel d'utilisateur télécharger pdf (Page 47)

Rev. 1.0

Principles of Operation 4—7

The frequency synthesizer also produces a lock signal. This signal is inverted and

buffered to produce both lock and unlock status signals for use in other parts of the

transmitter.

An FSK signal (used for automatic identification of FM repeaters) shifts the

frequencies of the 10.24–MHz crystal reference and the VCO. With keying, diodes in

the in the oscillator are reverse biased, increasing the crystal reference frequency. At

the same time, current through R358 increases the VCO frequency.

The digital management system is located on three boards:

• The metering board

• The metering daughter board

• Front panel controls and display

4.5.1 Metering Boards

The metering boards provide four functions:

• Scale operating parameters from various points in the transmitter to a propor-

tional DC voltage.

• Generate the ALC signal.

• Provide backup to the microprocessor controlled functions on the front panel.

• Provide real-time clock data for the fault log.

4.5.2 Front Panel

The digital management system front panel displays and controls all functions in

the transmitter. Scaled analog signals from the metering are converted to digital

format for display as selected by the operator. Selected values which were created

during a fault are stored for later recall in the fault-log. Real-time audio processing

and modulation is displayed on bar-graph displays; other parameters are displayed

on a four line alpha-numeric display.

Illustration 4-5 Metering Board

Metering

Board

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Crown FMX30 Manuel d'utilisateur Page 47