We report identification of the radio loud narrow-line quasar SDSS J172206.03+565451.6 which we found in the course of a search for radio loud narrow-line Active Galactic Nuclei ( AGN ) .
SDSS J172206.03+565451.6 is only the \sim 4th securely identified radio loud narrow-line quasar and the second-most radio loudest with a radio index R _ { 1.4 } \approx { 100 - 700 } .
Its black hole mass , M _ { BH } \simeq ( 2 - 3 ) \times 10 ^ { 7 } M _ { \odot } estimated from H \beta line width and 5100Å luminosity , is unusually small given its radio loudness , and the combination of mass and radio index puts SDSS J172206.03+565451.6 in a scarcely populated region of M _ { BH } - R diagrams .
SDSS J172206.03+565451.6 is a classical Narrow-Line Seyfert 1-type object with FWHM _ { H \beta } \simeq 1490 km/s , an intensity ratio of [ OIII ] /H \beta \simeq 0.7 and FeII emission complexes with FeII \lambda 4570/H \beta \simeq 0.7 .
The ionization parameter of its narrow-line region , estimated from the line ratio [ OII ] / [ OIII ] , is similar to Seyferts and its high ratio of [ NeV ] / [ NeIII ] indicates a strong EUV to soft-X-ray excess .
We advertise the combined usage of [ OII ] / [ OIII ] and [ NeV ] / [ NeIII ] diagrams as a useful diagnostic tool to estimate ionization parameters and to constrain the EUV–soft-X-ray continuum shape relatively independent from other parameters .