  Context. RR Gem is one of the few Blazhko RR Lyrae that has photometric
observations available extended enough to study the long-term courses of its
pulsation and modulation properties in detail.
  Aims. We investigate the pulsation and modulation properties and the
relations between them in RR Gem using photometric observations from the past
70 years in order to gain further insight into the nature of the Blazhko
modulation.
  Methods. We studied the photographic, photoelectric, and CCD light curves
obtained at the Konkoly Observatory and other authors' published maxima
observations. Detailed analysis of the light curves, maximum brightness, and
O-C data are carried out.
  Results. RR Gem showed modulation most of the time it was observed. The
modulation amplitude showed strong variations from the undetectable level (less
than 0.04 mag in maximum brightness) to about 0.20 mag. The amplitudes of the
amplitude and phase modulations showed parallel changes, thus the total 'power'
of the modulation have changed during the past 70 years. Parallel changes in
the pulsation and modulation periods occur with a d P_mod / d P_puls = 1.6 +/-
0.8 * 10^3 ratio. We also detected 0.05-0.1 mag changes in the mean maximum
brightness and mean pulsation amplitude.
