User's Manual

Digital ATSC Exciter-Modulator System Chapter 4, Axciter Modulator Detailed
Alignment Transmitter Set Up Procedures
Axcera Axciter, Rev. 0 49
Place the Transmitter into AGC by pushing the 3 of the keyboard entry on the Axciter
Upconverter Screen. This will place the Transmitter AGC into Auto.
(K2) Axciter Pre and Post Filter Sample Values
RF samples, to the external Axciter Relay, in a sled-based system, or to the rear of the
Upconverter/Downconverter tray, in a tray-based system:
These levels should be measured with a power meter before connecting them. Your
installation may require RF attenuators to be placed in line with the samples to get them
within the desired range.
J1 on the Relay or J17 on the Upconverter Tray is the connection to the Forward
power sample of the coupler before the mask filter, Pre-Filter Sample.
Level into the Relay at J1 or the Upconverter Tray at J17 should be 0 dBm to –10 dBm.
–5 dBm typical
J2 on the Relay or J16 on the Upconverter Tray is the connection to the Forward
power sample after the mask filter, Post-Filter Sample.
Level into the Relay at J2 or the Upconverter Tray at J16 should be 0 dBm to –10 dBm.
–5 dBm typical, but within .5 dB of the Pre-Filter sample.
Upconverter Down Converter Adjustment
On the Axciter Modulator, activate the Upconverter Main screen by selecting Upconverter
using the button next to it on the right side of the Axciter Main Screen. Activate the
Downconverter Output Gain by pushing 2 on the key board entry. Monitor the DTVision
Linear Display by pushing the button next to the DTVision Linear display on the right
side of the Axciter Main Screen. At the bottom of the DTVision linear screen, locate the
reading next to RMS. If this reading is between –10 dBm & 0 dBm no adjustment is
needed. If it is not, adjust the “Downconverter Gain”, then view the RMS value until it is
within the –10 dBm to 0 dBm range.
System Calibration of Forward and Reflected Powers Using the HX or LX
Driver/Amplifier, in Sled-Based Systems
NOTE: Perform the following procedures only if power calibration is suspect.
Forward Power Calibration
Check that transmitter is at 100% output power, as shown on the LCD display, on the
Control/Power Supply Sled in the Driver/Amplifier, with the display in the Set Up menus.
Measure with a VOM, TP31-14, Red, and TP31-12, Black, at the terminal block TP31
located on the rear chassis of the Driver/Amplifier Chassis Assembly. Adjust R9,
Forward Calibration Adjustment, on the Dual Peak Detector Board (1159965) for a
reading of .8VDC on the VOM. Locate the Forward Power Adjust screen, in the Set Up
menus of the LCD display on the Control/Power Supply Sled in the Driver/Amplifier, and
adjust the up or down arrow as needed to achieve 100 % output power.
This completes the forward power set up.