The NIST Noise Project has completed reconstruction of their 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 been in existence prior to this technical note, enough modifications and improvements have been made to warrant a new discussion. This note will briefly review the original system, discuss the theory as well as the design, testing, and capabilities of the present system. A more detailed uncertainty analysis is included and an appendix for troubleshooting the system.
Citation: Technical Note (NIST TN) - 1525
NIST Pub Series: Technical Note (NIST TN)
Pub Type: NIST Pubs
noise, noise measurement, noise temperature, radiometer, thermal noise