  We present radio observations of a region in the vicinity of the young pulsar
PSR B1853+01 in the supernova remnant W44. The pulsar is located at the apex of
an extended feature with cometary morphology. We argue on the basis of its
morphology and its spectral index and polarization properties that this is a
synchrotron nebula produced by the spin down energy of the pulsar. The geometry
and physical parameters of this pulsar-powered nebula and W44 are used to
derive three different measures of the pulsar's transverse velocity. A range of
estimates between 315 and 470 km/s are derived, resulting in a typical value of
375 km/s. The observed synchrotron spectrum from radio to X-ray wavelengths is
used to put constraints on the energetics of the nebula and to derive the
parameters of the pulsar wind.
