(λ ≈ 0.93 mm). The tropospheric oxygen's bands at 60 GHz (λ ≈ 5.00 mm) and 118.74 GHz (λ ≈ 2.52 mm) also affect the upper limit. To tackle the issue of water vapour, many observatories are built at high altitudes where the climate is more dry. However, not many things can be done to avoid the oxygen's interference with radio waves propagation. Radio frequency interference The width of the radio window is also affected by radio frequency interference which hinders the observations at certain wavelength ranges and undermines the quality of the observational data of radio astronomy. See also Infrared window Optical window Radio propagation References Electromagnetic spectrum