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The Comtech EF Data CDM-625A Advanced Satellite Modem is a high-performance, bandwidth-optimized, and cost-efficient modem engineered for mission-critical satellite communications. Designed to maximize spectral efficiency and minimize operational costs, the CDM-625A integrates advanced technologies such as DoubleTalk® Carrier-in-Carrier®, VersaFEC® and VersaFEC-2 LDPC coding, Adaptive Coding and Modulation (ACM), and an advanced packet processor with QoS and compression.
At VSATplus, we supply the Comtech CDM-625A with full configuration support, integration guidance, and global delivery. This modem is ideal for telecom operators, satellite service providers, government and military networks, offshore connectivity, and enterprise backhaul applications.
The CDM-625A builds on Comtech’s legacy of highly reliable satellite modems and introduces multidimensional optimization techniques to reduce both CAPEX and OPEX .
This modem is widely deployed for:
DoubleTalk Carrier-in-Carrier allows the transmit and receive carriers of a duplex link to overlap and share the same transponder bandwidth .
As shown in the diagram on page 2 of the datasheet, traditional full-duplex links place carriers adjacent in frequency. DoubleTalk overlaps them, creating a composite carrier while maintaining signal integrity.
The patent-pending CnC-APC compensates for rain fade automatically while maintaining total composite power .
It also allows link margin sharing between sites, enhancing availability.
The CDM-625A supports:
VersaFEC-2 provides up to 38 ModCods (long block) and 36 ModCods (short block) .
Compared to traditional TPC coding, LDPC can provide 0.7 to 1.2 dB additional coding gain .
ACM dynamically adjusts modulation and coding based on link conditions .
The modem includes:
This reduces external hardware requirements and simplifies deployment.
The optional high-performance Packet Processor provides:
| Parameter | Specification |
|---|---|
| Data Rate | 18 kbps – 25 Mbps |
| Symbol Rate | 18 ksps – 12.5 Msps |
| Frequency | 50–180 MHz (std), 950–2250 MHz (opt) |
| Rolloff | 5%, 10%, 15%, 20%, 25%, 35% |
| Modulation | BPSK, QPSK/OQPSK, 8PSK, 16-QAM, 32-ARY |
| FEC | Viterbi, RS, TCM, TPC, LDPC, VersaFEC, VersaFEC-2 |
| Parameter | Specification |
|---|---|
| Output Power | 0 to -25 dBm (70/140 MHz), 0 to -40 dBm (L-Band) |
| Frequency Stability | ±0.06 ppm |
| BUC Reference | 10 MHz via TX IF |
| BUC Power | 24V or 48V options |
| Parameter | Specification |
|---|---|
| Input Power | -105 + 10log(Rs) to -70 + 10log(Rs) dBm |
| Acquisition Time | ~120 ms at 64 kbps R1/2 QPSK |
| Adaptive Equalizer | 5-tap |
| Clock Tracking | ±100 ppm |
| Parameter | Specification |
|---|---|
| Form Factor | 1RU Rackmount |
| Dimensions | 1.75” x 19” x 17.65” |
| Weight | 10.8 lbs (4.9 kg) |
| Operating Temp | 0° to 50°C |
| Storage Temp | -40° to 85°C |
High efficiency with ACM and PTP support for LTE/5G timing.
Reduced antenna and amplifier size requirements.
Packet processor ensures optimized IP transport.
Adaptive equalizer and Doppler support enhance performance.
✔ DoubleTalk Carrier-in-Carrier bandwidth savings
✔ VersaFEC-2 high-performance LDPC
✔ Integrated Ethernet switch
✔ Advanced QoS & compression
✔ Wide range of data interfaces
✔ IEEE 1588v2 PTP timing support
✔ 1:1 and 1:10 redundancy options
✔ Backward compatible with CDM-625
VSATplus offers:
Our engineering team ensures correct selection of options such as VersaFEC-2, Packet Processor, DoubleTalk activation, and redundancy switching systems.
The Comtech CDM-625A Advanced Satellite Modem represents a powerful solution for operators seeking maximum spectral efficiency, advanced coding gain, and optimized IP transport. With Carrier-in-Carrier bandwidth compression, high-performance LDPC coding, adaptive modulation, integrated Ethernet switching, and comprehensive redundancy support, it delivers exceptional value across enterprise, telecom, offshore, and government satellite networks.
For organizations seeking to optimize transponder utilization while reducing infrastructure costs, VSATplus supplies the Comtech CDM-625A with full technical support and global delivery. Contact VSATplus today to order this advanced satellite modem and enhance your network performance.
