  In this paper we present the first observations of a large sample of
millisecond pulsars at frequencies of 2.7 GHz and 4.9 GHz. Our new flux
measurements extend the known spectra for millisecond pulsars to the highest
frequencies to date. The coverage of more than a decade of radio spectrum
allows us for the first time to search for spectral breaks as so often observed
for normal pulsars around 1 GHz. We align the observed millisecond pulsar
profiles with data from lower frequencies. Deviations from a dipolar magnetic
field structure are not evident and absolute timing across the wide frequency
range with a single dispersion measure is possible. We seem to observe mainly
unfilled emission beams, which must originate from a very compact region. A
compact emission region is also suggested by a remarkably constant profile
width or component separation over a very wide frequency range. For a few
sources, polarization data at 2.7 and 4.9 GHz could also be obtained which
indicate that millisecond pulsars are weakly polarized or even unpolarized at
frequencies above 3 GHz. The simultaneous decrease in degree of polarization
and the constant profile width thus question proposals which link
de-polarization and decreasing profile width for normal pulsars to the same
propagation effect (i.e. birefringence). Comparing the properties of core and
conal like profile components to those of normal pulsars, we find less
significant patterns in their spectral evolution for the population of
millisecond pulsars. Hence, we suggest that core and conal emission may be
created by the same emission process. In general, MSP emission properties tend
to resemble those of normal pulsars only shifted towards higher frequencies.
