[The Chicago Radio Laboratory started using the Z-Nith brand, a play on the company’s “9ZN” radio call letters, in 1920, as seen in the ad in the top left corner. The other ads above are promoting the company’s Model 4R Long Distance Receiver, 1923, which is part of our museu...
Bull Géodésique 15:247–251 Schüler T (2014) The TropGrid2 standard tropospheric correction model. GPS Solut 18:123–131 Thayer GD (1974) An improved equation for the radio refractive index of air. Radio Sci 9:803–807 Tregoning P, Herring TA (2006) Impact of a priori zenith ...
Bull Géodésique 15:247–251 Schüler T (2014) The TropGrid2 standard tropospheric correction model. GPS Solut 18:123–131 Thayer GD (1974) An improved equation for the radio refractive index of air. Radio Sci 9:803–807 Tregoning P, Herring TA (2006) Impact of a priori zenith ...