Comtech EF Data SDM-2020 - Manual (Page 20)

SDM-2020 Satellite Modulator Revision 7
Introduction MN/SDM2020M.IOM
1-4
The modulator incorporates concatenated error correction coding for improved signal
quality. With concatenated coding, an outer Reed-Solomon Codec is used in tandem with
an inner Viterbi or trellis-type Codec. The Reed-Solomon coding is DVB (based on 204,
188, t=8 type code), while the Viterbi and trellis codes are based upon a constraint length
K = 7 convolutional coding. This combination significantly reduces the required
operating power of the satellite system.
The modulator is a complete, self-contained unit in a standard, one-unit (1U) 19-inch
(48.26 cm) rack-mountable enclosure. It includes a backlit LCD display and a standard
Comtech EF Data 6-button keypad for user control.
A status and control port (available through a 9-pin D connector at the rear of the chassis)
provides either serial EIA-232 or EIA-485 for remote control applications. A second rear-
panel 9-pin D connector provides fault/alarm status.
The unit is designed to meet stringent safety and RF emissions standards, including CE
Mark certification.
1.2 A
SSEMBLIES
1.2.1 M
ODULATOR
The modulator consists of the assemblies listed in Table 1-2.
Table 1-2. Comtech EF Data Module Part Numbers
Part Number Description
PL/8200-1 SDM-2020 Top Assembly
PL/3995-39 IF Module, 75 Ω
PL/5612 Modulator Assembly
PL/3995-40 IF Module, 50 Ω
KT/8200 Chassis Assembly