Data Sheet Chapter 5

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UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures

LX Series, Rev. 0 5-1

Chapter 5

Detailed Alignment Procedures

This transmitter was aligned at the

factory and should not require additional

adjustments to achieve normal operation.

This transmitter takes the baseband

audio and video inputs or, if the

(Optional) 4.5-MHz composite input kit is

purchased, either a single composite

video + 4.5-MHz input or separate

baseband video and audio inputs, and

converts them to the desired UHF On

Channel RF Output at the systems output

power level.

The exciter/amplifier of the LX Series

transmitter is of a Modular design and

when a Module fails that module needs to

be changed out with a replacement

module. The failed module can then be

sent back to Axcera for repair. Contact

Axcera Customer Service Department at

724-873-8100 or fax to 724-873-8105,

before sending in any module.

5.1 Module Replacement

Module replacement on the LX series

products is a relatively simple process.

All modules plug directly into the

backplane board except for the power

amplifier module, and in higher power

units, the power supply and power

amplifier modules, that plug into a blind

mating connector. To replace a module,

refer to the following procedure.

Loosen the two grip lock connectors,

located on the front panel, at the top

and bottom of the module,

counterclockwise until the module

releases. The Modulator, IF Processor,

Upconverter and Controller/Power

Supply can then be gently pulled from

the unit. There are two cables

connected to the rear of the Power

Amplifier Module in the exciter/amplifier

chassis assembly. These two cables

must first be removed before the PA

module will slide out.

After removal of the failed module, slide

the replacement module in place and

make certain it connects to the

backplane board. If the replacement

module is a PA Module replace the two

cables on the rear of the

exciter/amplifier chassis assembly. If

the replacement module does not slide

in easily, verify it is properly aligned in

the nylon tracks, located on both the top

and bottom of the module.

Note: Each Module has an assigned slot

and will not fit properly in the incorrect

slot. Do not try to place a Module in the

wrong slot as this may damage the slot

or the connectors on the backplane

board.

Each module has the name of the

module on the front, bottom for

identification and correct placement.

The Modules are placed in the unit from

left to right; (1) Blank panel, (2)

Modulator (for analog transmitters) or a

Blank panel for a Translator or digital

transmitter, (3) IF Processor, (4)

Upconverter, (5) Controller/Power

Supply and (6) Power Amplifier.

5.1.1 Initial Test Set Up

Check that the RF output at the coupler

is terminated into a dummy load of at

least 100 watts. While performing the

alignment, refer to the Test Data Sheet

for the transmitter and compare the final

readings from the factory with the

readings on each of the modules. The

readings should be very similar. If a

reading is way off, the problem is likely

to be in that module.

Switch On the main AC for the system.

Summary of content (6 pages)

PAGE 1
UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures Chapter 5 Detailed Alignment Procedures This transmitter was aligned at the factory and should not require additional adjustments to achieve normal operation. After removal of the failed module, slide the replacement module in place and make certain it connects to the backplane board. If the replacement module is a PA Module replace the two cables on the rear of the exciter/amplifier chassis assembly.
PAGE 2
UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures 5.2 LX Series Exciter/Amplifier Chassis Assembly following details the meaning of each LED: This transmitter operates using the baseband audio and video inputs or, if the (optional) 4.5-MHz composite input kit is purchased, either a single composite video + 4.5-MHz input or separate baseband video and audio inputs. AURAL UNLOCK (DS5) – Red Indicates that 4.5 MHz Aural IF is unlocked from the Nominal 45.75 MHz visual IF.
PAGE 3
UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures MONO SET UP: The modulator was factory set for a ±25-kHz deviation with a mono, balanced, audio input of +10 dBm. If the reading is not at the correct level, adjust the MONO Audio Gain pot R110, located on the front panel of the modulator, as necessary, to attain the ±25-kHz deviation on the front panel screen. • DS4 (Mute) – Indicates that a Mute command is present to the system. Switch the transmitter to Standby.
PAGE 4
UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures Module. The adjustments are threshold settings that are adjusted as needed to correct for any amplitude or phase intermod problems. Adjust the top linearity correction adjustment R211 threshold cut in for the in phase amplitude distortion pre-correction that is needed. Next adjust the middle linearity correction adjustment R216 threshold cut in also for the in phase amplitude distortion pre-correction that is needed.
PAGE 5
UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures Control board, for 0% visual output. Perform the following adjustments with no aural present by removing the aural IF carrier jumper on the back of the chassis assembly. Connect a sync and black test signal to the video input jack of the test modulator. Switch the transmitter to Operate. R163 on the power amplifier module to a 10% reading. A reflected power fault should be present on the LCD Display.
PAGE 6
UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures the Outer Sleeve and the Center Rod of the Notch can be adjusted to tune the Notch Frequency. The Depth of the Notch is set by the gap between the Center Conductor of the Trap Section and the Center Conductor of the Main Line. Tight Coupling makes a Deep Notch, while Loose Coupling makes a Shallow Notch. Center Conductor with an Allen Wrench and move it Deeper for a Lower Frequency Notch or out for a Higher Frequency Notch.