NIST 30/60 MHz Tuned Radiometer for Noise Temperature Measurements

摘要

The NIST Noise project has completed reconstruction of its 30/60 MHz tuned, coaxial (Type N) radiometer system. This system is used at low frequencies, where isolators are impractical to incorporate. Without isolators, the ambient and cryogenic standards are tuned to the impedance of the device under test to minimize mismatches. Although this system had existed prior to publication of this technical note, enough modifications and improvements have been made to warrant a new report. This note will briefly review the original system, and discuss the theory as well as the design, testing, and capabilities of the present system. More detailed uncertainty analyses as well as details of system troubleshooting are also included.