  We use the cannonball (CB) model of gamma ray bursts (GRBs) to predict the
spectral and temporal behaviour of their radio afterglows (AGs). A single
simple expression describes the AGs at all times and frequencies; its
high-frequency limit reproduces the successful CB model predictions for optical
and X-ray AGs. We analyze all of the observed radio AGs of GRBs with known
redshifts, including those of the exceptionally close-by GRB 980425. We also
study in detail the time-evolution of the AGs' spectral index. The agreement
between theory and observations is excellent, even though the CB model is
extremely frugal in the number of parameters required to explain the radio
observations. We propose to use the scintillations in the radio AGs of GRBs to
verify and measure the hyperluminal speed of their jetted CBs, whose apparent
angular velocity is of the same order of magnitude as that of galactic pulsars,
consistently measured directly, or via scintillations.
