Comtech EF Data SDM-309B - Manual (Page 14)

MN/U-SDM309B Rev. # 1-1–1
Chapter 1.
INTRODUCTION
1.1 Scope
This manual describes the SDM-309B Satellite Modem, hereinafter referred to as the
modem (Figure 1-1). It includes installation, operation, and maintenance instructions. A
description of the equipment is contained in Section 1. Section 2 provides the installation
instructions. The use of controls, indicators, and operation is described in Section 3.
Maintenance instructions are in Section 4.
1.2 Purpose And Function
The modem is a high performance, full-duplex, QPSK digital modulator-demodulator for
Intelsat Business Services (IBS) satellite communication systems. This modem and
internal channel unit complies with the requirements of IESS 309. The internal channel
unit interfaces between SCPC fixed-rate terminal equipment having a data rate of 64
Kbps to 2.048 Mbps and adds overhead/framing to the data. The modem interfaces
between the channel unit and IF converter equipment operating in a 50 to 90 MHz or 100
to 180 MHz band (Figure 1-2). This modem can be used with an external channel unit
(Multipoint/M1200 or equivalent). Refer to Appendix C for more information. The
modem contains built-in scrambler/ descrambler, differential encoder/decoder, transmit
and receive frequency synthesizers, and a multi-rate Forward Error Correction (FEC)
convolutional encoder-viterbi decoder. The modem provides high performance with
narrow occupied bandwidth, automatic signal acquisition, high flexibility, and extensive
on-line monitoring circuits.
1.3 Description
The modem is a complete, self-contained unit in a standard 19-inch rack mountable
enclosure weighing approximately 25 pounds. It is of modular construction (Figure 1-3).
The chassis assembly (with the front and rear panel) encloses seven printed circuit board
assemblies (PCB). The backplane PCB is mounted on the chassis assembly and contains
receptacles for five plug-in PCB’s. Test points are located on the front board edge of the
modulator, demodulator, and decoder PCB. All controls and indicators for operation of