Block upconverter

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A Block Up Converter (BUC) 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.

Most BUCs use phase-locked local oscillators and require an external 10 MHz reference frequency to maintain the correct transmit frequency.

BUCs used in remote locations are often 2 or 4 W in the Ku Band and 5 W in the C Band. The 10 MHz reference frequency is usually sent on the same feedline as the main carrier. Many smaller BUCs also get their DC current over the feedline, using an internal DC block.

BUCs are generally used in conjunction with LNBs (Low Noise Blocks). The BUC, being an up-converting device, makes up the "transmit" side of the system, while the LNB is the down-converting device and makes up the "receive" side. An example of a system utilizing both a BUC and an LNB is a VSAT system, used for bidirectional internet access via satellite.