The variability of the tropical atmosphere at intraseasonal timescales is dominated by eastward propagating planetary scale disturbances confined to within 30 degrees south and north of the equator. Despite some progress from recent observational and modeling studies, the extent to which large shields of tropical clouds affect the existence of this phenomenon is still not fully understood. In order to better understand the role of cloud-radiative feedbacks in the Madden-Julian oscillation, we will present results from idealized climatological simulations with an aquaplanet general circulation model, which includes detailed parameterizations of cumulus convection, clouds and radiation. A recent study with an equatorial 2-D version of this model reports simulating MJO-like oscillations, which are replaced by somewhat faster modes when the cloud-radiative forcing is turned off or kept constant. We analyze the wave structure of the simulated fields in tropical channel experiments with and without cloud-radiative feedbacks and evaluate the role of the effective temperature profiles for the propagation of convectively coupled equatorial waves. We also plan to make wavenumber-frequency spectrum analyses of the outgoing longwave radiation fields from the model and to compare these with the corresponding results retrieved from satellite observations in the same region.