What Is Satcom and How Does It Relate to VSAT Satellite Communications?

Updated

Satcom (satellite communications) is the broad field of sending voice, video, and data through satellites in orbit. VSAT (Very Small Aperture Terminal) is one form of satcom: a network of compact earth stations—typically around 1.2 m to 2.4 m antennas—that connect to a hub or mesh and serve remote offices, vessels, vehicles, and field teams. In short, all VSAT is satcom, but not all satcom is VSAT; VSAT describes the small-terminal, often star-topology network model, while satcom also covers large earth stations, broadcast uplinks, and mobile SOTM (satcom-on-the-move) systems.

The core satcom link, in plain terms

Every satcom link has the same basic job: get a signal from a terminal up to a satellite, down to another terminal, and back. The equipment chain looks like this:

  • Antenna — focuses the signal. Fixed dishes for earth stations, compact flyaway antennas for SNG, flat-panel or stabilized antennas for vehicles and vessels.
  • BUC (Block Upconverter) — takes the modem's intermediate-frequency signal, shifts it up to the transmit band (Ku, Ka, X, etc.), and amplifies it. Power ratings (e.g., 4 W, 8 W, 100 W) determine link budget and antenna size trade-offs.
  • Modem — modulates and demodulates the carrier; modern IP satellite modems also handle routing, QoS, and bandwidth management.
  • LNB / L-band receive chain — downconverts the weak signal from the satellite to L-band for the modem or receiver.
  • Receivers and IRDs — for broadcast and video distribution, integrated receiver-decoders turn the downlink into usable video.
  • Supporting RF gear — splitters, fiber receivers, and monitoring equipment for larger stations.

A useful example: a remote mining camp needs internet and voice. The chain is a fixed Ku-band antenna, a BUC matched to the antenna gain, an IP satellite modem, and a router. Swap the fixed dish for a stabilized flat-panel antenna and the same modem/BUC logic applies—but now the terminal must track the satellite while the vehicle moves.

Satcom vs. VSAT: what actually differs

Dimension Satcom (general) VSAT
Scope All satellite communication Small-terminal networks within satcom
Terminal size From handheld to 10 m+ earth stations Roughly 0.75 m to 2.4 m class
Typical use Broadcast, teleports, backbone, mobile Remote offices, maritime, disaster response, SNG
Network model Point-to-point, broadcast, mesh Often hub-spoke, sometimes mesh
Equipment emphasis High-power amplifiers, large antennas Compact antennas, integrated modems, SOTM

The distinction matters when you specify equipment: a VSAT design starts from the terminal's size, power, and mobility, while a general satcom design may start from the earth station's EIRP and redundancy requirements.

Where satcom equipment is used

The product landscape on Digisat illustrates the range of applications:

  • Maritime — stabilized TV and communications antennas (e.g., Intellian marine satellite TV systems) for vessels.
  • Mobile and SOTM — flat-panel Ka-band antennas and vehicle-mount terminals for internet on the move.
  • SNG and flyaway — compact Ku-band flyaway antennas for newsgathering and rapid deployment.
  • Earth stations and teleports — pedestal-mount antennas, TWTAs, and L-band fiber distribution gear.
  • Remote connectivity — portable satellite internet systems with VSAT broadband service for field offices, telemedicine, government, and disaster response.

How to choose: start with four questions

  1. Frequency band — Ku, Ka, X, or L-band. Band choice drives antenna size, rain-fade margin, and BUC power. X-band and Ka-band military or government links have different regulatory and equipment constraints than commercial Ku.
  2. Terminal type — fixed, flyaway, vehicle-mount, or maritime stabilized. Mobility adds pointing and tracking requirements that fixed terminals don't have.
  3. Link budget — antenna gain plus BUC power plus modem efficiency must close the link at your required data rate. A 4 W BUC on a small antenna and a 100 W BUC on a large one serve very different throughput needs.
  4. Service and bandwidth — equipment alone doesn't deliver connectivity; you also need satellite capacity and a service arrangement. Confirm how bandwidth is provisioned before finalizing hardware.

Note that some items on the Digisat catalog show "Login To See Price" rather than a listed price, so budget planning may require a quote request rather than a direct cart purchase. Where prices are shown (for example, marine TV antennas and L-band splitters), they reflect the listed catalog price at the time of publication.

Practical takeaway

Treat "satcom" as the umbrella and "VSAT" as the small-terminal network pattern inside it. When you evaluate equipment, work backward from the application: band, mobility, data rate, and service contract. That sequence keeps antenna, BUC, and modem choices consistent instead of assembling parts that don't close the link.