VLA 8.4-GHz monitoring observations of the CLASS gravitational lens B1933+503

The complex 10-component gravitational lens system B1933+503 has been monit ored with the Very Large Array (VLA) during the period 1998 February-June w ith a view to measuring the time delay between the four compact components and hence to determine the Hubble parameter H-0. Here we present the result s of an 'A' configuration 8.4-GHz monitoring campaign that consists of 37 e pochs with an average spacing of 2.8 d. The data have yielded light curves for the four flat-spectrum radio components (components 1, 3, 4 and 6). We observe only small flux density changes in the four flat-spectrum component s that we do not believe are predominantly intrinsic to the source. Therefo re the variations do not allow us to determine the independent time delays in this system. However, the data do allow us to accurately determine the f lux density ratios between the four flat-spectrum components. These will pr ove important as modelling constraints and could prove crucial in future mo nitoring observations should these data show only a monotonic increase or d ecrease in the flux densities of the flat-spectrum components.