  About a dozen field RR Lyrae stars have been observed with the 24-inch
Heyde-Zeiss telescope of the Konkoly Observatory at Sv\'abhegy, Budapest, since
its refurbishment in 2003. Most of the observing time is allocated for the
investigation of the Blazhko modulation, a phenomenon that still does not have
a satisfactory explanation. The obtained multicolour CCD observations are
unique in extent. The accuracy of the measurements makes it possible to detect
low amplitude modulation of the light curve as well. The discovery of Blazhko
stars with low modulation amplitudes warns that the incidence rate of the
Blazhko modulation is, in fact, much larger than it was previously expected.
This makes the efforts exploring the cause of the modulation even more
important. A summary of our measurements and results achieved during the last 3
years is presented.
