User's Manual

Digital ATSC Exciter-Modulator System Chapter 4, Axciter Modulator Detailed
Alignment Transmitter Set Up Procedures
Axcera Axciter, Rev. 0 48
This transmitter operates using a SMPTE 310M input that connects to J27, the SMTE Input
Jack, located on the rear of the Axciter Modulator Tray. Check that the SMTE input is
present. If the (Optional) external 10 MHz input from the GPS is used, check that it is
connected to J9 on the Axciter Modulator.
The LCD screen, located at the front of the Control/Power Supply Module in the Exciter
Driver/Amplifier Assembly, controls the functional operation of the transmitter and in
turn the exciter.
The check of and the setup of the drive levels are completed using the LCD Display and
the front panel adjustments located on the Axciter Modulator Tray. The level of the RF
output which includes adjustment of the drive level of the Intermediate Power Amplifier
and the adjustment of the linearity and phase pre-distortion to compensate for any
nonlinear response of the Power Amplifiers are controlled within the Axciter Modulator
Tray.
Setting Up the Output Power of the Transmitter in Sled-Based System
The following adjustments are completed using the LCD screen located on the front
panel of the Axciter Modulator Tray. On the Axciter Main Screen, push the button next
to the Upconverter tab on the right side of the screen. This will open the Upconverter
Main Screen. Set the AGC to Manual by selecting 3 on the keyboard entry. The screen
will now indicate AGC Manual. Set the transmitter to full power using the
Driver/Amplifier LCD display while viewing the Power Control Screen in the Set Up Menu.
Setting up of AGC 1
To set up the AGC, first the AGC must be activated. Locate the 8 position DIP switch
SW1 mounted on the Control Board in the Axciter Upconverter Sled, mounted in the
Driver/Amplifier Chassis Assembly. The Upconverter DIP Switch Positions 6 and 8 must
be switched ON which allows the user to modify the AGC 1 and AGC 2 gain through the
Axciter Modulator.
On the Axciter Upconverter Screen, set AGC 1 to 1.5 Volts, by selecting 4 on the key
board entry. This will cause a detail screen to appear prompting you to enter a number
value. Monitor the AGC 1 Gain Value on the screen and increase or decrease the value
of the number entered until the monitored reading is 1.5 Volts.
Setting up of AGC 2
On the Axciter Upconverter Screen, set AGC 2 to 1.7 Volts, by selecting 5 on the
keyboard entry. This will cause a detail screen to appear prompting you to enter a
number value. Monitor the AGC 2 Gain Value on the screen and increase or decrease
the value of the number entered until the monitored reading is 1.7 Volts.
After the setting up of the AGC, the AGC must be de-activated to prevent accidental
changes. The Upconverter DIP Switch SW1 Positions 6 and 8 must be switched OFF
which locks the AGC 1 and AGC 2 gain.
Setting up of Overdrive Threshold
On the Axciter Upconverter Screen set the Overdrive Threshold to 1.6 Volts, by selecting
7 on the keyboard entry. This will cause a detail screen to appear. Increase or
decrease the voltage as needed until the monitored reading is 1.6 Volts.