  High brightness temperature radio transients such as pulsars and fast radio
bursts require the coherent radiation of particles. The antenna class of
coherent radiation models require a large number of charged particles radiating
in phase, therefore the particles must be spatially confined and have
well-aligned velocities. Given these necessary conditions, we look at the
magnetic field induced by the currents associated with coherently emitting
accelerated particles and consider the interaction between the radiating
particles and the induced magnetic field. We find a maximum luminosity of
coherent curvature radiation that depends on source parameters such as surface
magnetic field and neutron star spin period. We find that coherent radio
emission across all luminosities can be explained by coherent curvature
radiation and suggest it could be universally responsible for both FRBs and
extreme galactic sources. Using the Crab Pulsar as an example, we constrain the
emission parameters and origin of the most extreme nanoshots to within 60km of
the pulsar surface assuming coherent curvature radiation. In agreement with
recent observations, we also predict simultaneous X-ray emission from
small-scale particle gyration due to the induced field.
