Coaxial Relay (Optional Dual Excitation); Power Splitter; Uhf Power Amplification System - Hitachi EC702HP Operation Manual

Section 1 - Introduction (UHF Digital TV Transmitters)
E-Compact - Air Cooling - ATSC - High Power
The FI signal is then filtered and amplified, this feeds the output stage of AD conversion (Analog
to Digital) and the AGC level detector (Automatic Gain Control), which operates in the Truss
(Variable Voltage Controlled Attenuator) of the RF inputs (average power between 0 and +10dBm)
in order to maintain the output of FI with an average power of -5dBm + / - 1dB.
This signal is available for monitoring via test point connector and is also applied to the drivebuffer
that feeds the AD converter, which operates clocked at 86.09790209 MHz and 16 bits resolution.

1.4.5.2 Coaxial Relay (Optional Dual Excitation)

The UHF coaxial relay makes the selection of which exciter (A or B) will provide the signal to the
passive splitter, which distributes the signal to the power drawers. This switch is controlled by a
DC command from the exciter A.The software present on this unit makes the control and selection
of which exciter will be transmitting. The exciter which is not selected will remain powered in
standby, ready to take control of the equipment.

1.4.5.3 Power Splitter

This passive module is a UHF power splitter in quadrature, which is responsible for the clustering
of power drawers in parallel configuration. Receives the signal from the exciter and promotes a
division 1:N

1.4.5.4 UHF Power Amplification System

The amplification system comprises power drawers PA708HP model (MOD GV40001)
combined to obtain the final output power. Each drawer provides 860W from 8 power amplifier
in configuration Doherty power amplifier configuration, in this way one obtains a high efficiency
amplifier. Power drawers are mounted in the rack via a quick release system which allows
speed in maintenance operation.
The main features of the power drawer are:
 High efficiency
 Doherty Configuration
 Standing fans accessible from the front panel
 Removable power supply at the rear panel of the drawer
 3U Power Drawer for 19" rack
( 5)
*
N represents the number of drawers of the transmitter.
( * 6)
The EC701HP equipment uses the MOD GV 40087 drawer. What differs from the drawer MOD GV 40001 are
the models of adders and back panel connectors.
Manual Rev. 0.0 - April 2016
(*5) , to excite the UHF amplifiers in the drawer power.
Figure 1-7 - Splitter
(UHF 2-Way Hybrid Splitter - QS2C - used in
the EC702HP transmitter)
(*6)
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