March 25, 1999
Noise temperatures of the GBT Q-band array receiver prototype were measured on March 18. The amplifiers installed in the dewar at this time were 5-stage units (SN Q32 and Q33) with an input InP HFET and four Rohm Research GaAs HFETS. Hot/Cold measurements were done using absorbers in styrofoam containers - one at ambient temperature and one in a liquid nitrogen bath. Tests at 40-45 GHz were at an IF center frequency of 3000 Mhz and bandwidth of 1280 Mhz. Tests at 46-50 GHz were at an IF center frequency of 6000 Mhz and bandwidth of 1280 Mhz. An HP power meter was used to detect the total power and measure Y-factors. The chart below shows results of these tests: