  We present follow-up spectroscopy and photometry of 11 post common envelope
binary (PCEB) candidates identified from multiple Sloan Digital Sky Survey
(SDSS) spectroscopy in an earlier paper. Radial velocity measurements using the
\Lines{Na}{I}{8183.27,8194.81} absorption doublet were performed for nine of
these systems and provided measurements of six orbital periods in the range
$\Porb= 2.7-17.4$ h. Three PCEB candidates did not show significant radial
velocity variations in the follow-up data, and we discuss the implications for
the use of SDSS spectroscopy alone to identify PCEBs. Differential photometry
confirmed one of our spectroscopic orbital periods and provided one additional
\Porb measurement. Binary parameters are estimated for the seven objects for
which we have measured the orbital period and the radial velocity amplitude of
the low-mass companion star, $K_\mathrm{sec}$. So far, we have published nine
SDSS PCEBs orbital periods, all of them $\Porb<1$ d. We perform Monte-Carlo
simulations and show that $3\sigma$ SDSS radial velocity variations should
still be detectable for systems in the orbital period range of $\Porb\sim1-10$
days. Consequently, our results suggest that the number of PCEBs decreases
considerably for $\Porb>1$ day, and that during the common envelope phase the
orbital energy of the binary star is maybe less efficiently used to expell the
envelope than frequently assumed.
