| The emission of pulsars at low radio frequencies ({dollar}<{dollar}50 MHz) presents several unique characteristics which are related to the configuration and physical conditions of the magnetosphere at large distances from the neutron star. However, the existing data at low radio frequencies is scarce, due to the lack of adequate instruments and to intrinsic difficulties in carrying out the observations. The dissertation project was aimed at observing and studying several intense, low-dispersion, long-period pulsars, using the University of Chile 45 MHz radiotelescope and the University of Florida 26.3 MHz radiotelescope.; A total of eleven pulsars were observed at 45 and 26.3 MHz. Pulsars 0031-07, 0628-28, 0826-34, 0834+06, 0950+08, and 2045-16 were detected at 45 MHz. Pulsars 0834+06, 1508+55, and 1919+21 were detected at 26.3 MHz. All these pulsars were observed with one- or two-channel receivers and narrow bandwidths. Long term integration was used in order to improve the signal-to-noise ratio of the pulses. The data were digitized at sampling rates between 32 and 100 Hz.; The basic parameters measured for the detected pulsars were the integrated pulse profile, pulse width, pulse flux density and energy, delay of arrival times at two different frequencies, and the detection of subpulses and interpulses. The dispersion measure was computed using the delay of arrival times of the integrated pulse profiles. A collection of integrated pulse profiles for each of the detected pulsars is included.; The measurements obtained at 45 and 26.3 MHz were compared with already published low frequency data. The results obtained in this dissertation were discussed in the context of current models of the pulsar magnetosphere.; The results of the observations are consistent, within the context of the polar cap model, with emission originating in the distorted magnetic field at a distance comparable to the radius of the velocity-of-light cylinder. |
