Polarization of radio sources. IV. The compact source PKS 2134 + 004

Data on flux, circular polarization, linear polarization, and angular size for apparently simple, nonvariable compact radio sources are brought together and analyzed in an attempt to restrict the range of possible models. Three such sources are investigated: PKS 2134+004, PKS 0237-23, and PKS 1148 - 00. All three are found to show strong evidence of a significantly nonhomogeneous structure. A plausible model is one in which the main part of the flux is produced in a core, while the linear polarization originates in a shell that is thin both optically and to Faraday rotation. Part of the observed circular polarization may be produced by Faraday pulsation from the relativistic electrons in the sources. Subject headings: polarization - quasi-stellar sources or objects - radio sources