  We calculate intensity and angular power spectrum of the cosmological
background of synchrotron emission from cold dark matter annihilations into
electron positron pairs. We compare this background with intensity and
anisotropy of astrophysical and cosmological radio backgrounds, such as from
normal galaxies, radio-galaxies, galaxy cluster accretion shocks, the cosmic
microwave background and with Galactic foregrounds. Under modest assumptions
for the dark matter clustering we find that around 2 GHz average intensity and
fluctuations of the radio background at sub-degree scales allows to probe dark
matter masses >100 GeV and annihilation cross sections not far from the natural
values <sigma v> ~ 3 x 10^(-26) cm^3/s required to reproduce the correct relic
density of thermal dark matter. The angular power spectrum of the signal from
dark matter annihilation tends to be flatter than that from astrophysical radio
backgrounds. Furthermore, radio source counts have comparable constraining
power. Such signatures are interesting especially for future radio detectors
such as SKA.
