VSAT terminology.

Written by Tom on Wednesday 14/03/07


I have just got a VAST Internet connection installed and running at the school I’m working at.


There was a bit of a learning curve involved in getting my head around the complete system. Here is a list of new TLA’s and others that I learnt.



BUC: Block Up Converter, is used in the transmission (uplink) of satellite signals. It converts a band (or "block") of frequencies from a lower frequency to a higher frequency. Modern BUCs convert from the L band to Ku band, C band and Ka band. Older BUCs convert from the 70 MHz band to Ku band or C band.



Copol ver’s Xpol: Co-Polarized ver’s Cross Polarized.
You can get look at both of them here.


Diplexers: generally differ from Duplexers in that Diplexers are generally used to separate whole frequency ranges while Duplexers tend to separate small frequency differences. For example, a certain Diplexer may have two output ports, and one input port. Port A (Input), port B (Output 1) and port C (output port 2). Port A may be connected to a device that produces multiple frequency ranges, for example HF (High Frequency - Less then 30 MHz) and say VHF (Very High Frequency - 130 MHz - 174 MHz). The Diplexer might be used to separate these two "bands" (HF & VHF) into to different antenna. In our example port B may handles all frequencies below 50 MHz while port C handles those frequencies above 50 MHz.


EIRP: Effective Isotropic Radiated Power is a figure of merit for the net radiated power in a given direction. It is equal to the product of the power supplied to a transmitting antenna and the antenna gain in a given direction relative to an isotropic radiator, expressed in Watts.


IDU: In Door Unit, The NetModem in our case iDirect 3100.


LNBs: Low Noise Blocks, is the receiver (downlink) on the dish.


NOC: Network Operations Centre: This is the ground base for the provider.


ODU: Out Door Unit, dish, LNB, BUC.


VSAT: Is short for Very Small Aperture Terminal, an earthbound station used in satellite communications of data, voice and video signals, excluding broadcast television. A VSAT consist of two parts, a transceiver that is placed outdoors in direct line of sight to the satellite and a device that is placed indoors to interface the transceiver with the end user's communications device, such as a PC.