A simple two-channel solar radiometer and data retrieval technique is described for sensing the columnar content of atmospheric water vapor via differential solar transmission measurements in and adjacent to the 940 nm water vapor absorption band. The instrument features two parallel channels for simultaneous measurements in and out of the absorption band to eliminate temporal variability effects in the differential comparison of the data from the two channels. The water vapor transmittance is determined by a modified Langley plot analysis of the ratio of the two channel signals. A statistical band model which closely follows the square-root law is then used to extract the columnar water vapor amount from the water vapor band transmittance. Water vapor retrievals obtained by this simple ratio analysis and band model generally agree to within 10% with radiosonde measurements.