14. Radio and extreme-ultraviolet observations of CF Tucanae Gunn A. G., Migenes V., Doyle J. G., Spencer R. E., MNRAS, 1997, 287, 199. Compressed Postscript (8441 kbytes) PDF (1912 kbytes) ABSTRACT. We present contemporaneous EUV and radio observations obtained for the totally eclipsing chromospherically active RS CVn-type binary CF Tucanae. Observations were made with the ATNF Compact Array at 6 cm and 3.6 cm over one complete orbital cycle of the system and with the EUVE Deep Survey/Spectrometer telescope over five orbital cycles. We obtained a strong detection of the source (1.9 mJy at 6 cm and 1.1 mJy at 3.6 cm) in the radio. Both EUV and radio flux levels appear to show a clear modulation at the orbital period with a maximum at phase 0.5 which indicates the existence of an intra-binary region of activity. This has important consequences for the details of coronal formation and field interaction in active close binary stars. We interpret the EUV emission as an isotropically radiating thermal source; on the other hand the radio emission shows evidence of intrinsic gyromagnetic directivity. We also demonstrate that contemporaneous EUV and radio observations are not sufficient to determine the characteristics of the gyroemission electron population.