Spacek Labs Model CS-K Low-Noise COLFET Calibration Source offers a new way to calibrate K-band radiometers. Instead of a liquid nitrogen-cooled load, a small waveguide-output source (K-connector optional) radiates 33-60 K over 20-24 GHz when biased by +8 VDC, 100 mA max. The CS-K operates at room temperature so no cooling is required. Its voltage regulator ensures the constant noise temperature output, and can also be TTL controlled. Also available are high-temperature output noise sources providing ~20 dB ENR when biased. The high-ENR and COLFET noise sources are available for K-band water radiometers and for V-band covering 50-60 GHz for oxygen-line radiometers.