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Section 1 - Introduction (UHF Digital TV Transmitters)
E-Compact - Air Cooling - ATSC - High Power
1.4.5.7 Filtering System
The TV transmitter is endowed with a filtration system that ensures that the spectral conformity
of the TV channel broadcast on UHF stay in accordance with the parameters set by international
standards (FCC, ITU and Anatel).
The filtering system of the transmitter consists of two steps:
Low-pass UHF filter
Bandpass filter
The low-pass filter has the form of a rigid line, which aims to counter the harmonics of second
and third order of the TV signal broadcasted on UHF.
(
6)
*
Note: Each transmitter uses a given filter model bandpass filter and low-pass model.
1.4.5.8 RF Sampling Probe
Measured Module, we used to extract a signal sample to perform measurements with the
transmitter installed and operating, without this being necessary to remove the operation
transmitter. This module provides points of RF samples for RF measurements with spectrum
analyzer, direct power measurement with Power Meter (reflectometer) and analysis of digital
modulation ATSC.
It has three RF couplers (sample) matched with RF levels defined, and is also used to measure
reflected power (reflectometer) by sampling probe set for this purpose.
1.4.5.9 Power Supplies
The power supplies used in the TV transmitters are all the switching type. These power supplies
are controlled by the digital control units via the shutdown command. Also report, each in its
respective control unit, the DC voltage supplied and the consumption required by UHF amplifiers'
transistors.
In the transmitter, three models of power supplies are used:
- Module 4779 - Exciter power supply
- Module 40008 - Power Drawer's Power Supply (MOD GV 40001 / MOD GV 40087)
- Module 40039 - AC Unit
Manual Rev. 0.0 - April 2016
1-18
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