  We present high-sensitivity multi-frequency radio continuum observations of
the starburst galaxy NGC~2146. We have fitted these data with a
three-dimensional diffusion model. The model can describe the radio emission
from the inner disk of NGC~2146 well, indicating that diffusion is the dominant
mode of propagation in this region. Our results are indicating that NGC~2146
has recently undergone a starburst, the star forming activity being located in
a central bar. The spatial variation of the radio emission and of the spectral
index yield tight constraints on the diffusion coefficient $D_0$ and the energy
dependence of the diffusion. Away from the central bar of the galaxy the radio
emission becomes filamentary and the diffusion model was found to be a poor fit
to the data in these regions; we attribute this to different transport
processes being important in the halo of the galaxy.
