6.5 Receiver

The receivers amplify the signal. Most VLBA receivers are HFETs (Heterostructure Field Effect Transistors) at a physical temperature of 15 K, but the 90 cm and 50 cm receivers are GaAsFETs (Gallium Arsenide FETs) at room temperature. Each receiver has 2 channels, in opposite circular polarizations. The 1 cm, 7 mm, and 3 mm receivers also perform an initial frequency down conversion.