User's Manual

Innovator CHV400BTD ATSC Transmitter Board Descriptions
Technical Manual, Rev. 0 49
Circuit Descriptions of Boards in the CHV200B System
(A1) 8 VSB Demodulator Board (1308275) - Only used with BRD operation
Overview
The 8 VSB demodulator assembly receives an off air 8 VSB signal on any VHF or UHF
channel and demodulates this to an MPEG-2 transport stream that is per the SMPTE-
310M standard. The input to the assembly is at an “F” style connector on the shielded
tuner and can be at a level of –8 to –78 dBm. The tuner (TU1) down converts the RF
channel to a 44 MHz IF signal. This signal is the input to the digital receiver chip U1.
The digital receiver chip subsequently decodes the IF and delivers an MPEG-2 transport
stream on a parallel data bus to a programmable logic array, U8. U8 clocks the
asynchronous MPEG data from the receiver chip and outputs a synchronous data stream
at a 19.39 MHz rate to buffer/driver U11. U11 subsequently drives the output at J13 to
a lower level that is AC coupled out of the board.
Microcontroller Functions
A microcontroller, U17, is provided on this assembly to supervise the operation of the
receiver chip and the tuner. In addition, the microcontroller also interfaces to the front
panel LCD display via connector J24 and pushbutton interface on J27. On power up, the
microcontroller sets the tuner to the last channel that was selected when the unit was
powered down. In addition, the microcontroller also configures the digital receiver to
operate as an 8 VSB receiver. The communication between all of the devices on this
board is via an I2C serial bus that is local to this board.
Jumper and DIP Switch Settings
This board can be used in various assemblies. When this assembly is installed in the
Innovator CXB product, the jumpers on J7 and J8 should be placed between pins 2 and 3
for normal operation. The DIP switch SW1 should be configured as indicated in Table
12.
Table 12: Innovator CX Receive /Demodulator/Transcoder Dip Switch SW1
Position Function When Switch is Off When Switch is On
SW1-1 Tuner Type
Original Tuner
(DTT765xx)
Recent Tuner (DTT7680x)
SW1-2 Signal Strength Gain Gain = 8.0 Gain = 9.3
SW1-3 Special Channel Plan Normal
Channels 2, 3, or 4 are offset
up 4 MHz
SW1-4 Reserved for Future
SW1-5 Reserved for Future
SW1-6 Reserved for Future
SW1-7 Reserved for Future
SW1-8 Operation Type Transcoder Operation Innovator CX/CXB Operation
NOTES: SW1-8 operation is available in software versions greater than or equal to 2.3
with hardware versions greater than or equal to D0, unless the board was factory
modified.
These switch positions are factory set for your system and should not be changed.