  (Abridged) S147 is a large faint shell-type supernova remnant (SNR). Its
remarkable spectral break at cm-wavelengths is an important physical property
to characterize the SNR evolution. However, the spectral break is based on
radio observations with limited precision. We made new radio continuum and
polarization observations of S147 at 11cm and at 6cm with the Effelsberg 100-m
telescope and the Urumqi 25-m telescope, respectively. These new data were
combined with published lower frequency data from the Effelsberg 100-m
telescope and very high frequency data from WMAP to investigate the spectral
turnover and polarization properties of S147. S147 consists of numerous
filaments embedded in diffuse emission. We found that the integrated flux
densities of S147 are 34.8+/-4.0 Jy at 11cm and 15.4+/-3.0Jy at 6cm. These new
measurements confirm the known spectral turnover at ~1.5GHz, which can be
entirely attributed to the diffuse emission component. The spectral index above
the turnover is -1.35+/-0.20. The filamentary emission component has a constant
spectral index over the entire wavelength range up to 40.7GHz of -0.35+/-0.15.
The weak polarized emission of S147 is at the same level as the ambient diffuse
Galactic polarization. The rotation measure of the eastern filamentary shell is
about -70 rad/m2. The filamentary and diffuse emission components of S147 have
different physical properties, which make S147 outstanding among shell type
SNRs.The weak polarization of S147 at 11cm and at 6cm can be attributed to a
section of the S147 shell showing a tangential magnetic field direction.
