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Comtech EF Data CDM-600 Digital Satellite Modem

The CDM-600 is an Open Network modem, fully compliant with IESS-308, 309, and 310, with data rates up to 20 Mbps. Data rates up to 2 Mbps are standard rates up to 8448 and 20 Mbps are an extra-cost option.

The CDM-600 and CDM-600L are open network satellite modems, which are fully compliant with IESS-308, -309, -310, -314, and -315 from 64 kbps through T2 and E2. They are available in the following three data rate ranges:

  • Low-Rate variable: 2.4 kbps to 5.0 Mbps
  • Mid-Rate variable: 2.4 kbps to 10.0 Mbps
  • High-Rate variable: 2.4 kbps to 20.0 Mbps

In addition, both modems operate in closed network from 2.4 kbps to 10 Mbps. The modems include T1, E1, T2, and E2 G.703 interfaces, in addition to EIA-422, V.35, EIA-232, and serial LVDS. HSSI is provided by adding the CIC-20 interface converter.

The architecture is firmware and FPGA-based, and the internal Flash memory allows easy updating via the serial port. The modem offers exceptional flexibility and performance in a 1RU enclosure.

CDM-600 Rear Panel

  • CDM-600: 50 to 90 or 100 to 180 MHz IF range
    CDM-600L: 950 to 1950 MHz IF range
  • Fast acquisition demodulator (±32 kHz acquisition range, 64 kbps, Rate 1/2 QPSK: 1 sec average)
  • BPSK, QPSK, OQPSK, 8-PSK, 16-QAM modulation types
  • Data rate range from 2.4 kbps to 5 Mbps
  • Forward Error Correction choices include Turbo Product Coding (IESS-315 compliant), Viterbi, Sequential, Reed-Solomon, LDPC, and TCM
  • Intermediate Data Rate (IDR)
  • Intelsat Business Services
  • D&I++
  • ESC++
  • Automatic Uplink Power Control (AUPC)
  • Embedded Distant-end Monitor and Control (EDMAC)
  • Asymmetric Loop Timing
  • CDM-600: 50 or 75O, front panel selectable
    CDM-600L: Transmit 50O, Receive 50 or 75O, female Type N connector
  • Open network compatible and backwards compatible with the CDM-500/CDM-550, and CDM-550T
  • Interoperable with SDM-300A, SDM-300L3 (CDM-600L only)
  • 1:1 and 1:10 redundancy switch available

Feature Enhancements

Enhancing the modem's performance is easy. Additional features are added quickly on site, using FAST access codes purchased from Comtech EF Data. To enable these features, simply enter the code at the front panel.

Turbo Product Coding

The modems offer all traditional FEC methods and incorporate an optional Turbo Product Codec (TPC). TPC is a FEC technique that delivers significant performance improvement when compared to Viterbi with concatenated Reed-Solomon. TPC simultaneously offers increased coding gain, lower decoding delay, and significant bandwidth savings.

Two TPC codecs are offered as hardware options:

  • The Low-Rate TPC codec operates up to 5 Mbps with limited code rates.
  • The High-Rate TPC codec operates up to 20 Mbps, and offers a full range of code rates (5/16 through 7/8, and 0.95) with all modulation types from BPSK to 16-QAM

EDMAC Operation

A special feature of the modems are their ability to monitor and control the distant end of a satellite link using a Comtech EF Data proprietary overhead channel. This framed mode is called EDMAC (Embedded Distantend Monitor and Control). User data is framed and extra bits are added to pass control, status, and Automatic Uplink Power Control information. This process is completely transparent to the user. An RF transceiver (C-Band and Ku-Band) or Block Up Converter at the distant end of a satellite link may be controlled and monitored from the front panel of the modem using a low data rate FSK signal on the Rx IF cable via the EDMAC channel.

Remote Control

The operator may configure and monitor the modem from the front panel, or through the remote M&C port. Ten complete configurations may be stored in the modem. An event log stores alarm and status information in non-volatile RAM, while the Link Statistics log stores link performance (Eb/No and AUPC performance) for QoS reporting purposes. SatMac, a Windows-based monitor and control program, is available for configuring the local and distant end modems, transceivers, and redundancy switches.

Low Density Parity Check (LDPC) Coding and 8-QAM Modulation

A third codec is available as a hardware option. The TPC/LDPC Codec combines all TPC functions of the High Rate TPC option, plus the following new features:

  • Improved performance of LDPC codes at 1/2, 2/3, and 3/4 rates to further improve coding gain and bandwidth efficiency.
  • 8-QAM modulation that offers the same bandwidth efficiency of 8-PSK but with improved BER performance and tracking in noisy environments.

Drop and Insert (D&I++)

Full Drop and Insert functionality is available as an option. The modems offer two variants of Drop and Insert (D&I). The first is an Intelsat Open Network-compliant mode, using the IBS framing (6.7%). The second is CEFD's Proprietary Enhanced mode, called D&I++. This "n" x 64 kbps mode offers any value of "n" up to 24, and permits the simultaneous use of EDMAC, AUPC (see below) and an ESC circuit at 1/576th of the user data rate. This is achieved with the addition of only 2.2% overhead.


A high rate overhead channel is now standard in the new enhanced version of the modems. This provides a separate RS- 232 channel allowing up to 4.8 kbaud at 64 kbps and up to 38.4 kbaud at 512 kbps. AUPC also operates in this mode.