We consider the compact (≲ 2–4 asec) radio sources in the 3CR catalogue with normal (α ≲ 0.5) straight spectrum and low frequency (νc≲ 200 MHz) turnover. The curvature in the spectrum, if due to synchrotron self-absorption, implies structures of the order of tenths of an arcsec, while its straightness at high frequencies suggests that no dominant very compact (∼1 mas) feature is present. The radio sources matching the above requirements are listed in the Table. The sample is probably not complete but it is representative of the class.