We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728 , 1382 and 3100 MHz .
The observations at 728 and 3100 MHz were conducted simultaneously using the dual-band 10-50cm receiver .
These high-sensitivity , multi-frequency observations provide a systematic and uniform sample of pulsar flux densities .
We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars .
Using techniques from robust regression and information theory we classify the observed spectra in an objective , robust and unbiased way into five morphological classes : simple or broken power law , power law with either low or high-frequency cut-off and log-parabolic spectrum .
While about 79 \% of the pulsars that could be classified have simple power law spectra , we find significant deviations in 73 pulsars , 35 of which have curved spectra , 25 with a spectral break and 10 with a low-frequency turn-over .
We identify 11 gigahertz-peaked spectrum ( GPS ) pulsars , with 3 newly identified in this work and 8 confirmations of known GPS pulsars ; 3 others show tentative evidence of GPS , but require further low-frequency measurements to support this classification .
The weighted mean spectral index of all pulsars with simple power law spectra is -1.60 \pm 0.03 .
The observed spectral indices are well described by a shifted log-normal distribution .
The strongest correlations of spectral index are with spin-down luminosity , magnetic field at the light-cylinder and spin-down rate .
We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars .