  4C 71.07 is a high-redshift blazar whose optical radiation is dominated by
quasar-like nuclear emission. We here present the results of a spectroscopic
monitoring of the source to study its unbeamed properties. We obtained 24
optical spectra at the Nordic Optical Telescope (NOT) and William Herschel
Telescope (WHT) and 3 near-infrared spectra at the Telescopio Nazionale Galileo
(TNG). They show no evidence of narrow emission lines. The estimate of the
systemic redshift from the H$\beta$ and H$\alpha$ broad emission lines leads to
$z_{\rm sys}=2.2130 \pm 0.0004$. Notwithstanding the nearly face-on orientation
of the accretion disc, the high-ionization emission lines present large
broadening as well as noticeable blueshifts, which increase with the ionizing
energy of the corresponding species. This is a clear indication of strong
ionized outflows. Line broadening and blueshift appear correlated. We applied
scaling relationships to estimate the mass of the supermassive black hole from
the Balmer and C IV lines, taking into account the prescriptions to correct for
outflow. They give $M_{\rm BH} \sim 2 \times 10^9 \, M_\odot$. We derived an
Eddington luminosity $L_{\rm Edd} \sim 2.5 \times 10^{47} \rm \, erg \, s^{-1}$
$\sim L_{\rm disc}$, and a broad line region luminosity $L_{\rm BLR} \sim 1.5
\times 10^{46} \rm \, erg \, s^{-1}$. The line fluxes do not show significant
variability in time. In particular, there is no line reaction to the jet
flaring activity detected in 2015 October and November. This implies that the
jet gives no contribution to the photoionization of the broad line region in
the considered period.
