  The dc transport properties of long arrays of small Al Josephson junctions,
biased through on-chip Cr resistors, are studied. The IV-characteristics show a
large Coulomb threshold for current as well as negative-slope regions
indicating the regime of autonomous Bloch oscillations up to rather high
frequencies of f = I/2e ~1 GHz, comparable to those reported by other groups
for single junctions. On the other hand, a small depth of the back-bending
implies a low duty cycle and a broad spectrum of the oscillations, which we
attribute to the insufficiently high impedance of the bias resistors. A
self-sustained switching process at a small bias current is used to study the
statistics of the switching voltages and to determine the effective Bloch
capacitance which was found to considerably exceed the geometric junction
capacitance.
