The evolution of classical doubles: clues from complete samples

We describe the inter-dependence of four properties of classical double radio sources - spectral index, linear size, luminosity and redshift - from an extensive study based on spectroscopically-identified complete samples. We use these relationships to discuss aspects of strategies for searching for radio galaxies at extreme redshifts, in the context of possible capabilities of the new generation of proposed radio telescopes.
Comment: To appear in `Perspectives in Radio Astronomy: scientific imperatives at cm and m wavelengths.' eds: M.P. van Haarlem and J.M. van der Hulst Version with colour figures available at http://www-astro.physics.ox.ac.uk/~kmb