  We present radio observations and modelling of one of the nearest and
brightest Type IIP supernova SN\,2004dj exploded in the galaxy NGC 2403 at a
distance of $\sim$ 3.5 Mpc. Our observations span a wide frequency and temporal
range of 0.24 - 43 GHz and $\sim 1$ day to 12 years since the discovery. We
model the radio light curves and spectra with the synchrotron emission. We
estimate the mass-loss rate of the progenitor star to be $\dot{M}$ $\sim$ 1
$\times$ 10$^{-6}$ M$_{\odot}\, \rm yr^{-1}$ for a wind speed of 10
km\,s$^{-1}$. We calculate the radio spectral indices using 1.06, 1.40, 5.00
and 8.46 GHz flux density measurements at multiple epochs. We witness
steepening in the spectral index values for an extended period predominantly at
higher frequencies. We explain this as a signature of electron cooling
happening at the supernova shock in the plateau phase of the supernova. We
estimate the cooling timescales for inverse Compton cooling and synchrotron
cooling and find that inverse Compton cooling is the dominant cooling process.
