SLM-3650 Comtech EF Data Satellite Modem

The Comtech EF Data SLM-3650 Satellite Modem has been designed to communicate with all the world's major satellite systems, including the Defense Satellite Communications Systems (DSCS). The units have an extended range of microprocessor-controlled functions to implement advanced, high-level coding techniques such as Reed-Solomon (RS) FEC for superior performance.

The SLM-3650 includes Fully Accessible System Topology (FAST) enhancement features.

The SLM-3650 is compatible with the OM-73, MD-1002, SLM-6650, SLM-8650, SDM-650, LM-46/4046, and MD-945 within the data rate limitations specified for those modems. The INTELSAT/EUTELSAT option provides compatibility with PTT earth stations worldwide. A fully operational SLM-3650 can be configured to operate with many existing commercial and proprietary modems by selecting specific parameters via the front panel keypad or remote control.

The SLM-3650 can be used on DSCS, SKYNET, NATO, PANAMSAT, and all U.S. domestic satellites. Options extend the modem range to include EUTELSAT and INTELSAT satellite networks. The SLM-3650 is the ideal equipment solution when implementing Tri-band terminals that require both commercial and government communication access.

The modem is configured to derive timing from either the data clock or a 1, 5, 10 or 20 MHz station clock. The interface type is MIL-STD-188 and accepts balanced differential pairs for data and clock. The data and clock also meet the requirements for EIA-422.

The SLM-3650 can be equipped with the necessary baseband processors to operate with Intermediate Data Rate (IDR), INTELSAT Business Service (IBS), or SMS earth stations worldwide. The open network mode also supports fractional T1 or E1 transmission.

The SLM-3650 can be equipped with an optional Asynchronous Overhead/Automatic Uplink Power Control (AUPC). Operation in the SLM-3650-02 mode adds overhead bits to the data stream for an over-the-satellite communications link. This link can be used to monitor and control the equipment at a remote site. For the AUPC mode, some of the overhead bits of the frame are used to establish a modem-to-modem control link. Thresholds and limits can then be set to automatically compensate for fades. The AUPC mode requires another similarly equipped Comtech EF Data modem operating on the opposite end.

8-PSK operation can significantly increase the capacity of the satellite link. A 2 Mbps circuit may be increased to 2.6 Mbps when changing from QPSK 3/4 with R-S to 8-PSK 2/3 with R-S. Both configurations have equal bandwidth on the satellite transponder. More signal power is required for the satellite to achieve the desired bit error performance.