User's Manual

Theory of Operation GMH Series VHF Radio
Page 4-6 BK RADIO
4.3.5 Control Board
Control Board functions include:
1. Microprocessor Control
2. EEPROM storage
3. Regulation
4. Display Driver
5. Signaling
6. Audio Power Amplifier
4.3.5.1 Microprocessor Control
U102 controls the interface between the radio and the user. During normal operation, U102 monitors the
front panel and push-to-talk switches, and provides data to the display. In the radio programming mode,
U102 interprets commands from the serial bus and provides a transparent interface to the external
programming source.
4.3.5.2 EEPROM Storage
EEPROM U105 is used to store the radio configuration and channel information, i.e., receive and transmit
frequencies and code guard values for each channel.
4.3.5.3 Regulation
A switching regulator, U103, is used to generate +32 volts for the vacuum fluorescent display and driver. A
+5 volt regulator, U108, is used to supply power requirements for the control and options boards.
4.3.5.4 Display Driver
Display driver U100 receives data to be displayed from U102 and drives the vacuum fluorescent display.
4.3.5.5 Signaling
U206 generates audible and subaudible tones (such as CTCSS).
4.3.5.6 Audio Power Amplifier
The audio amplifier, U107, can deliver a maximum of 4 watts into a 3.2 ohm load. Audio muting is provided
by U109.