  We have observed pulsar wind nebulae in the three supernova remnants
G11.2-0.3, G16.7+0.1, and G29.7-0.3 at 89 GHz with the
Berkeley-Illinois-Maryland Association Array, measuring total flux densities of
two of them for comparison with archival data at other frequencies . In
G16.7+0.1, we find a break in the spectrum of the PWN at ~26 GHz. In G29.7-0.3,
our data suggest a break in the integrated spectrum of the central nebula at
~55 GHz, lower than previously estimated. However, we have found spatial
structure in the spectrum of this nebula. The emission to the north of pulsar
J1846-0258 has a broken spectrum, with break frequency ~< 100 GHz, consistent
with a conventional pulsar-powered nebula. The emission to the south of the
pulsar has a near-power-law spectrum from radio to X-rays: this component may
be unrelated to the PWN, or may be evidence of asymmetries and/or time
evolution in the pulsar's energy output. We present 89 GHz images of each
remnant.
