The four known pulsating radio sources1,2 have all been observed at wavelengths down to 32 cm (ref. 3). For the source CP 1919 an upper limit to the flux density at 21 cm (ref. 4), a positive detection at 13 cm (ref. 5), and an upper limit at 11 cm (ref. 6) have been published. The previous observations at 11 cm wavelength have now been extended to all four sources, and positive results are reported here for two of them.