Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Uncertainties in NIST Noise-Temperature Measurements



James P. Randa


Uncertainty analyses are presented for NIST measurements of noise temperature. All systems currently used in NIST calibrations of thermal-noise sources are treated. These include tuned systems for 30 and 60 MHz, coaxial total-power radiometers for 1 to 12 GHz, a switching radiometer for the WR-90 (8.2 to 12.4 GHz) waveguide band, and total power waveguide radiometers for the WR-62 (12.4 to 18 GHz), WR-42 (18 to 26.5 GHz), WR-28 (26.5 to 40 GHz), and WR-15 (50 to 75 GHz) bands. Measurements through adapters are also analyzed. Typical expanded (k = 2) uncertainties for the measurements are in the range 0.7 percent to 1.4 percent, depending on the particular system and the frequency.
Technical Note (NIST TN) - 1502
Report Number


noise, noise measurement, noise temperature, thermal noise, uncertainty analysis


Randa, J. (1998), Uncertainties in NIST Noise-Temperature Measurements, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 24, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created March 1, 1998, Updated February 19, 2017