  Due to the decrease in cost, size and weight, \acp{UAV} are becoming more and
more popular for general-purpose civil and commercial applications. Provision
of communication services to \acp{UAV} both for user data and control messaging
by using off-the-shelf terrestrial cellular deployments introduces several
technical challenges. In this paper, an approach to the air-to-ground channel
characterization for low-height \acp{UAV} based on an extensive measurement
campaign is proposed, giving special attention to the comparison of the results
when a typical directional antenna for network deployments is used and when a
quasi-omnidirectional one is considered. Channel characteristics like path
loss, shadow fading, root mean square delay and Doppler frequency spreads and
the K-factor are statistically characterized for different suburban scenarios.
