User's Manual

300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures
DT830A, Rev. 1 5-11
REFERENCE
DESIGNATOR
FUNCTION SETTING
SW2
4-position DIP switch: Used
to adjust the gain of the
linear equalizer when J28 is
set to 1-2.
Divide – Sw 1,2
On, On – divide by 1
On, Off – divide by 2
Off, On – divide by 4
Off, Off – divide by 8
Divide – Sw 3,4
On, On – multiply by 1
On, Off – multiply by 1.25
Off, On – multiply by 1.5
Positions 1-4: All positions should
remain off during normal
operation.
The last adjustment on the symbol
generator card is the LCD contrast. This
potentiometer, R32, can be adjusted
until the desired level of contrast
appears on the front panel display.
5.3.3 (A5) VSB Filter Board (1561-
1301; Appendix D)
The VSB filter board performs the digital
pulse-shaping filter function of the ATSC
specification. The board receives
equalized symbol data at J1 and applies
it to an in-phase (I) pulse-shaping filter
and a quadrature (Q) pulse-shaping
filter. The I filter is implemented in U1
and U2 and the Q filter is implemented
in U3 and U4. The pulse-shaping filter
outputs are applied to digital-to-analog
(D/A) converters through jumper blocks
J25 and J28. The output of the D/A
converters is filtered to remove the
32.28-MHz converter update rate. The I
data are available at J26 and the Q data
are available at J29.
Note: The 8-VSB filter board
contains jumper blocks and
adjustment potentiometers which
have been set at the factory. No
additional alignment is required to
achieve normal operation.
In the event that the board becomes
incorrectly aligned, the jumpers on the
board should be placed in the
configurations shown in Table 5-5.