  We describe a simple scenario of inflationary magnetogenesis based on a
helical coupling to electromagnetism. It allows to generate helical magnetic
fields of strength of order up to $10^{- 7}\,\text{G}$, when extrapolated to
the current epoch, in a narrow spectral band centered at any physical
wavenumber by adjusting the model parameters. Additional constraints on
magnetic fields arise from the considerations of baryogenesis and, possibly,
from the Schwinger effect of creation of charged particle-antiparticle pairs.
