  We have conducted a multiwavelength survey of 42 radio loud narrow-1ine
Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources
of this type and omitting those with steep radio spectra. We analyse data from
radio frequencies to X-rays, and supplement these with information available
from online catalogs and the literature in order to cover the full
electromagnetic spectrum. This is the largest known multiwavelength survey for
this type of source. We detected 90% of the sources in X-rays and found 17% at
gamma rays. Extreme variability at high energies was also found, down to
timescales as short as hours. In some sources, dramatic spectral and flux
changes suggest interplay between a relativistic jet and the accretion disk.
The estimated masses of the central black holes are in the range $\sim
10^{6-8}M_{\odot}$, smaller than those of blazars, while the accretion
luminosities span a range from $\sim 0.01$ to $\sim 0.49$ times the Eddington
limit, similar to those of quasars. The distribution of the calculated jet
power spans a range from $\sim 10^{42.6}$ to $\sim 10^{45.6}$ erg s$^{-1}$,
generally lower than quasars and BL Lac objects, but partially overlapping with
the latter. Once normalised by the mass of the central black holes, the jet
power of the three types of active galactic nuclei are consistent with each
other, indicating the scalability of the jet. Despite the observational
differences, the central engine of RLNLS1s is apparently quite similar to that
of blazars. The historical difficulties in finding radio-loud narrow-line
Seyfert 1 galaxies might be due to their low power and to intermittent jet
activity.
