  The ARCADE radio excess and EDGES measurement remain puzzling. A link between
the two has been previously considered, however, in this work we highlight an
important related effect that was not analyzed in detail before. By performing
cosmological thermalization calculations with soft photon injection using {\tt
CosmoTherm}, we show that for the 21 cm signal generation the interplay between
enhanced radio spectral distortions and the associated heating can hide a
significant radio excess before the reionzation era. We illustrate this effect
for a simple power-law soft photon source in decaying particle scenarios. Even
if simplistic, the uncovered link between CMB spectral distortions and 21 cm
cosmology should apply to a much broader range of scenarios. This could
significantly affect the constraints derived from existing and future 21 cm
observations on the evolution of the ambient radio background. In particular,
scenarios that would be ruled out by existing data without heating could become
viable solutions once the heating is accounted for in the modelling. Our
calculations furthermore highlight the importance of global 21 cm observations
reaching into the dark ages, where various scenarios can potentially be
distinguished.
