System Description Chapter 2

ManualsBrandsUBS-Axcera ManualsElectronicsUHF television transmitter

3-kW UHF Transmitter Chapter 2, System Description

835-3, Rev. 0 2-4

Chapter 2

System Description

The 834-3 is a complete 3-kW UHF solid-state, internally diplexed television transmitter

that operates at a nominal visual output power of 3000 watts peak of sync and average

aural output power of 300 watts, at an A/V ratio of 10 dB.

2.1 System Overview

The 835-3 is made up of two cabinets: a UHF exciter cabinet (the left cabinet) and an

amplifier array cabinet (the right cabinet).

This 835-3 (1176-1527) is comprised of (A1) a UHF exciter assembly (1227-1200), (A2)

an amplifier array assembly (1245-1700), (A9) a bandpass filter (2005-1064), (A10) an

output trap filter assembly, and (A11) an output coupler assembly (1020-1002).

The left cabinet contains (A1) the UHF exciter assembly (1227-1200) for the 3-kW

transmitter, mounted at the top of the cabinet.

The (A2) 3-kW amplifier array assembly (1176-1528) contains (A9-A1) an 8-way

splitter (ZFSC-8-43), (A9-A2) an ALC splitter board (1181-1002), six (A1 through A6)

600-watt amplifier trays (1227-1300), (A7) a 6-way combiner, (A12) a reject load

assembly (1278-1312), (A10) an AC distribution panel (1245-1300), and (A11) an

interface panel.

Switch S2 is an Automatic/Manual switch that controls the operation of the transmitter

by the presence of the video input signal. When the switch is in Automatic, the green

LED DS3 is lit and, if the video input signal to the transmitter is lost, the transmitter will

automatically switch to Standby. When the video input signal returns, the transmitter

will automatically switch back to Operate. In Manual, the amber LED DS4 is lit and the

operation of the transmitter is controlled by the front panel switches. During normal

operation of the transmitter, switch S2 should be in the Automatic position. The front

panel of the UHF exciter also has LEDs that indicate an overtemperature fault, (red LED

DS6), an ALC fault, (red LED DS8), a video fault (loss) (red LED DS9), and a VSWR

cutback (amber LED DS7).

The (A1) UHF exciter (1227-1200) takes the baseband audio and video inputs and

produces a diplexed, modulated, and on-channel frequency visual + aural RF output.

The RF output of the UHF exciter at J15 is connected to (A2) the 3-kW amplifier

assembly (1245-1700), where it is split six ways in (A9-A1) the 8-way power splitter

assembly (ZFSC-8-43). The outputs of the splitter feed the six (A1, A2, A3, A4, A5, and

A6) 600-watt amplifier trays (1227-1300) that amplify the RF signals to approximately

600 watts each.

A forward power sample from the 4-way combiner board inside the 600-watt amplifier

tray is connected to the dual peak detector board. This board provides a peak-detected

forward sample to the amplifier control board that supplies the sample to the front panel

meter of the 600-watt amplifier tray. Before exiting each 600-watt amplifier tray, the

RF is fed through a circulator for protection of the tray from high VSWR conditions. The

reject port of the circulator provides a reject sample to the 4-way combiner board that

supplies the reflected sample to the dual peak detector board. The peak-detected

reflected sample connects to the amplifier control board that provides the sample to the

front panel meter of the tray. The outputs of the six 600-watt amplifier trays are then

Summary of content (5 pages)

PAGE 1
3-kW UHF Transmitter Chapter 2, System Description Chapter 2 System Description The 834-3 is a complete 3-kW UHF solid-state, internally diplexed television transmitter that operates at a nominal visual output power of 3000 watts peak of sync and average aural output power of 300 watts, at an A/V ratio of 10 dB. 2.1 System Overview The 835-3 is made up of two cabinets: a UHF exciter cabinet (the left cabinet) and an amplifier array cabinet (the right cabinet).
PAGE 2
3-kW UHF Transmitter Chapter 2, System Description combined in (A7) a 6-way combiner that provides approximately 3400 watts peak of sync output. The combined output of the amplifier assembly is connected to (A9) a bandpass filter, (A10) an output trap filter, and then to (A11) the output coupler assembly (1020-1002). The bandpass filter and trap filter are tuned to provide high outof-band rejection of unwanted products.
PAGE 3
-kW UHF Transmitter Chapter 2, System Description The RF input from the UHF exciter tray connects to J1 on (A11) the interface panel in the amplifier assembly. The RF is connected to the COM input of (A9-A1) the 8-way splitter which splits it eight ways; six of the outputs are connected to J1, the RF input on each of the 600-watt amplifier trays (1227-1300), and the other two outputs are terminated with 50-Ω loads.
PAGE 4
3-kW UHF Transmitter Chapter 2, System Description Note: If the transmitter does not switch to Operate when S1 is switched to Operate, check that a dummy jumper plug, with a jumper between pins 23 and 24, is connected to jack J11 on the rear of the UHF exciter tray. This jumper provides the interlock needed for the operation of the transmitter. If the interlock is present, the green LED DS5 on the transmitter control board should be lit.
PAGE 5
3-kW UHF Transmitter Chapter 2, System Description the AC distribution assembly (1247-1100) in the right, center rear of the cabinet. The assembly contains TB1, which connects to the 220 VAC (line 1 to TB1-1, line 2 to TB1-2, and ground to TB1-3). The AC distribution panel contains one circuit breaker that supplies the AC to the rest of the cabinet. The input AC is connected to CB1, the main AC circuit breaker (80 amps).