  We present the analysis of time-resolved spectroscopy of the pulsating sdB
star PG1605+072. From our main observing run of 16 nights we have detected
velocity variations at 5 frequencies that correspond to those found in
photometry. Based on these data, there appears to be change in amplitude of the
dominant modes over about a year. However, when we include extra observations
to improve the frequency resolution, we find that some of the frequencies are
split into two or three. Simulations suggest that the apparent amplitude
variation can be at least partially explained by a series of very closely
spaced frequencies around the two strongest modes. By combining observations
taken over ~300 days we conclude that some of the closely spaced modes are
caused by one mode whose amplitude is varying, however this frequency is still
within ~1 microHz of an apparently stable frequency. Because of this kind of
complexity and uncertainty we advise caution when trying to identify
oscillation modes in this star.
