Instruction Manual DM8-R Digital Modulator Tray AXCERA, LLC 103 FREEDOM DRIVE, P.O. Box 525 LAWRENCE, PA 15055-0525 USA (724) 873-8100 • FAX (724) 873-8105 www.axcera.com • info@axcera.
DM8-R Digital Modulator Tray Table of Contents DM8-R DIGITAL MODULATOR TABLE OF CONTENTS SECTION ...................................................................................................PAGE Overview ......................................................................................................2 Inputs and Outputs ........................................................................................2 Front Panel Interface .................................................................
DM8-R Digital Modulator Tray Tray Description DM8-R Modulator Tray Overview The DM8-R modulator Tray is an ATSC compliant 8 VSB modulator that mounts in a standard 19” rack. The DM8-R modulator accepts a SMPTE-310 MPEG data stream and outputs a 6 MHz wide IF output centered at 44 MHz with a pilot carrier at 46.69 MHz. The DM8-R modulator provides linear and nonlinear correction capability for the transmission path as well as internal test sources that are used during initial transmitter installation.
DM8-R Digital Modulator Tray Board Descriptions DM8-R Modulator Board Configuration The Digital Modulator Board in the DM8-R is setup through a configuration header located on the board. The configuration header contains 8 jumper positions between pins on J26 and J27. The functions of these positions are given in Table 1.
DM8-R Digital Modulator Tray Board Descriptions Analog Output Section The baseband I and Q signals from the D/A converter are applied to differential analog filters that remove some of digital artifacts from the D/A conversion process. The output of the I channel filter is then mixed with the pilot frequency, 46.69 MHz, using mixer U30. The output of the Q filter is mixed with the pilot frequency that is phase shifted 90 degrees using mixer U34.
DM8-R Digital Modulator Tray Initial Set Up Initial Set Up The DM8-R Modulator Tray was set up at the factory for best digital response and correction for the transmitter and should require no customer adjustments to attain normal operation. The digital transmitter operates using an MPEG input that connects to J2 on the rear of the DM8-R Modulator Tray. The IF output of the DM8-R Modulator Tray, at J4, connects to the IF input jack located on the exciter for the transmitter.
DM8-R Digital Modulator Tray Drawing List DM8-R Modulator Tray Interconnect....................................................................................... 1306984 Digital Modulator, DT1D Board Schematic .......................................................................................... 1304884 DM8-R Front Panel Board Schematic .......................................................................................... 1307113 DM8-R Digital Modulator, Rev.
-VSB Modulator - DM8-R The DM8-R 8-VSB modulator accepts an ATSC-compliant SMPTE 310M digital bit stream. To modulate to the 8-VSB standard, the digital data stream is first randomized and then forward error corrected (FEC) through Reed-Solomon encoding, data field interleaving and trellis coding. The FEC signal processing minimizes data errors in the digital bit stream and reduces the chance of burst errors, while significantly improving the system coding gain.
8-VSB Modulator - DM8-R Mechanical General Modulation Type Symbol Rate Error Protection (Per ATSC Standard) Signal to Noise Ratio (SNR) Out of Band Rejection EVM Size (W x D x H) Weight 8-VSB 10.76 MHz RS(207, 187) t=10 Convolutional Interleaver 2/3 Rate Trellis Encoder 34 dB min (36 dB typical) 41 dB min (47 dB typical) 2.0% max (1.
