Multi-frequency analysis of the two CSS quasars 3C 43 & 3C 298

We present and discuss observations made with MERLIN and VLBI at 1.7 and 5 GHz of the two CSS quasars 3C 43 and 3C 298. They show quite different morphologies, the former being a very distorted triple radio source, the latter a small FRII type object. Relativistic effects and structural distortions are discussed. Source ages are evaluated to be of the order of $~rox 10^5 years, therefore 3C 43 and 3C 298 can be considered fairly ``young'' radio sources. Some inference is also derived on the properties of the medium surrounding the radio emitting regions in these sub-galactic objects, whose density could be as low as 10-3 cm-3.