UBS Axcera LU100AT User Manual

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.

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.

LX Series, Rev. 0 5-1

UHF Analog Driver/Transmitter Chapter 5, Detailed Alignment Procedures

5.2 LX Series Exciter/Amplifier
Chassis Assembly

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.

On the LCD Display, located on the
Controller/Power Supply Module, in
Transmitter Set-Up, push the button to
switch the transmitter to Operate. The
check of and the setup of the Audio and
Video input levels are completed using
the LCD Display and the front panel
adjustments on the Modulator assembly.
The level of the RF output includes
adjustments of the drive level to the
Power Amplifier and the adjustment of
the linearity and phase predistortion to
compensate for any nonlinear response
of the Power Amplifier. The adjustments
are located on the front panel of the IF
Processor module.

Modulator Module Assembly

NOTE: Not present in a Translator

systems.

The Modulator Assembly has adjustments
for video levels and audio modulation
levels, and other related parameters.

Connect an NTSC baseband video test
signal input (1 Vpk-pk) to the transmitter
video input jack J7 on the rear of the
tray. Jacks J7 and J17 are loop-through
connected; the J17 jack can be used as a
video source for another transmitter.
Connect a baseband audio input (+10
dBm) to the balanced audio input
terminal block TB02-1 [+], TB02-2 [-],
and TB02-3 [ground] or, if
stereo/composite audio is provided,
connect it to BNC jack J3, the composite
audio input jack.

Verify that all LEDs located on the front
panel of the Modulator are Green. The

following details the meaning of each
LED:

AURAL UNLOCK (DS5) – Red Indicates
that 4.5 MHz Aural IF is unlocked from
the Nominal 45.75 MHz visual IF.

VISUAL UNLOCK (DS6) – Red Indicates
that the Nominal 45.75 MHz visual IF is
unlocked from the 10 MHz reference.

AUDIO OVER DEVIATION (DS4) – Red
Indicates that the input Audio level is too
high. (±75 kHz max)

VIDEO LOSS (DS1) – Red Indicates that
the input Video level is too low.

OVER MODULATION (DS3) – Red
Indicates that the input Video level is too
high.

ALTERNATE IF (DS7) – Red Indicates
that an external Nominal 45.75 MHz IF is
not present to the modulator.

10 MHz PRESENT (DS2) – Red Indicates
that an external 10 MHz reference is not
present to the modulator.

Look at the front panel LCD meter on the
Control/Power Supply Module Assembly.
Set the LCD screen to the Modulator
Details video output level screen, the
screen indicates active video from 0 to 1
Vpk-pk. The normal video input level is 1
Vpk-pk on the front panel screen. If this
reading is not at the proper level, the
overall video level can be changed by
adjusting the VIDEO LEVEL control R42
on the front panel of the Modulator to the
1 Vpk-pk level on the front panel screen.

NOTE: An NTSC or FCC composite signal
should be used for video metering
calibration.

Switch the LCD display to the Modulator
Details screen that indicates the AUDIO
DEVIATION (modulation level) of the
signal up to 75 kHz.

LX Series, Rev. 0 5-2