Studies of weak compact radio sources

Approximately 20% of weak sources in a scintillation survey at 102 MHz were not identified in other, more sensitive, low-frequency surveys. These sour ces had very high compactness and steep spectra. Since, as shown earlier, t hese sources are probably quasars, the epoch of the radio birth of quasars should correspond to Bur densities of similar to 0.01 Jy. (C) 2000 MAIK "Na uka/Interperiodica".