This report addressed two technical risks associated with replacing current air traffic and weather surveillance radars with a single type of multifunction phased array radar (MPAR). The first risk is whether radio spectrum usage would increase with the MPAR network and whether the allocated band will have enough spectral space. This question is addressed in two steps. First, single-radar spectrum usage is estimated based on certain assumptions regarding the radar design. Second, locations based on a previous radar placement study are used together with a terrain-dependent propagation model to compute the number of frequency channels needed at each site. We conclude that the overall spectrum usage is likely to increase with MPAR, but that the targeted window in S band will be able to accommodate the occupancy at all sites. The second risk is whether self-interference will limit the ability of the MPAR to operate asynchronously and adaptively on different antenna faces. This question is addressed by employing a simple bistatic ground clutter model to characterize the interference between adjacent faces. We conclude that some interference is unavoidable, but it would likely only occur during times when a transmit beam is at its maximum off-broadside angle (~2% of the time).