  We propose a new technique to measure the time delay of radio-loud
gravitational lens systems, which does not rely on the excessive use of
interferometric observations. Instead, the method is based on single-dish flux
density monitoring of the (unresolved) lens system's total lightcurve, combined
with additional interferometric measurements of the flux density ratio at a few
epochs during that monitoring period. The basic idea of the method is to
reconstruct the individual image lightcurves from the observed total lightcurve
by assuming a range of potential values for the time delay and the
magnification ratio of the images. It is then possible to single out the
correct reconstruction, and therefore determine the time delay, by checking the
consistency of the reconstructed individual lightcurves with the additional
interferometric observations. We performed extensive numerical simulations of
synthetic lightcurves to investigate the dependence of the performance of this
method on various parameters which are involved in the problem. Probably the
most promising candidates for applying the method (and also for determining the
Hubble constant) are lens systems consisting of multiply imaged compact sources
and an Einstein ring, such as B0218+357 from which some of the parameters used
for our simulations were adopted.
