User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD Board Descriptions
ATSC Transmitter/Regenerative Translator
Instruction Manual, Rev. 1 61
using pots R2 and R3. The Diode CR1 provides temperature compensation for the
transistor. The transistor will output over 20 Watts DVB, but is typically used in a
driver application at much lower output powers. The Directional Coupler U1
provides a 20 dB down sample of the RF output.
(A6-A3) Dual 878 Pallet Assembly (1313170 or 1310138)
This board is a LDMOS UHF power amplifier consisting of two power transistors
operating in parallel. The board operates on a power supply voltage of +42 VDC.
The voltage regulator U1 steps down the voltage to provide a bias voltage to
each transistor. The diodes CR1 and CR3 are used to temperature compensate
the bias voltage. As the RF transistors heat up, the diodes also heat up, causing
the voltage across them to drop, lowering the bias voltage to the RF transistors
so that it remains constant with device temperature.
The board has a gain of approximately 17 dB, and can operate at an output
power of 150 Watts average power DVB, 220 Watts average power ATSC, or 440
Watts Peak Sync plus sound in analog operation. The transistors are operated in
quadrature, with one transistor operating 90 degrees out of phase of the other,
which provides for a very good return loss across the UHF band on both the input
and output of the board.
(A6) Amplifier Assembly w/888A devices (1316132 used w/External Axciter
Drawer or 1315381 used in all other applications) – Used in the CU0TD/RD-4 &
CU0TD/RD-5
The (A6) Amplifier Assembly (1316132) is made up of (A6-A1) the 1 Watt Amplifier
Board (1315730), (A6-A2) the BL881 Single Stage Amplifier Board (1314882, (A6-A3)
the Dual 888A Pallet Assembly (1315347) and (A6-A5) a DC-DC Converter Board
(1315335). The ALC Board (The ALC Board (1308570 is used in the 1315381 Assembly
& the 1315006 is used in the 1316132 Assembly) is also used with this assembly. The
entire amplifier assembly has approximately 36 dB of gain.
(A6-A1) 1 Watt UHF Amplifier Module (1315730)
This board is normally operated at a power of 200 mW pk sync or lower. It
consists of two AH202 MMICs operating in parallel. The board is powered by +12
VDC and has no adjustments. The amplifier module has a gain of approximately
17 dB.
(A6-A2) BLF881 Single Stage Amplifier Board (1314882)
This board consists of a single stage amplifier operating at +48 VDC. The board
has an overall gain of about 16 dB. The input to the board passes through a 3 dB
attenuator consisting of R11-R13, and then is applied to the gain stage, which
consists of a single LDMOS transistor Q1 operating in Class AB. The bias voltage
for the transistor is generated through the voltage regulator U1, and is adjusted
using pots R2 and R3. The Diode CR1 provides temperature compensation for the
transistor. The transistor will output over 40 Watts pk sync, but is typically used
in a driver application at much lower output powers. The Directional Coupler U2
provides a 20 dB down sample of the RF output at the SMA Jack J4.