  Wireless communication at millimeter wave frequencies has attracted
considerable attention for the delivery of high-bit-rate connectivity to
unmanned aerial vehicles (UAVs). However, conducting the channel measurements
necessary to assess communication at these frequencies has been challenging due
to the severe payload and power restrictions in commercial UAVs. This work
presents a novel lightweight (approximately 1.3 kg) channel measurement system
at 28 GHz installed on a commercially available UAV. A ground transmitter
equipped with a horn antenna conveys sounding signals to a UAV equipped with a
lightweight spectrum analyzer. We demonstrate that the measurements can be
highly influenced by the antenna pattern as shaped by the UAV's frame. A
calibration procedure is presented to correct for the resulting angular
variations in antenna gain. The measurement setup is then validated on real
flights from an airstrip at distances in excess of 300 m.
