An analysis of data from three years of monitoring of interplanetary scintillations in 2015–2017 during a phase of decreasing solar activity is presented. The observations were carried out on the Large Scanning Antenna of the Lebedev Physical Institute at 111 MHz. During the period considered, the spatial distriution of the scintillation level was close to spherically symmetrical, on average, and did not undergo any strong time variations on scales of months or years. The monthly-mean scintillation level is not correlated with theWolf number.

Results of long-term (2002–2010) monitoring of giant radio pulses of the pulsar PSR B0531+21 in the Crab Nebula at ν = 44, 63, and 111 MHz are reported. The observations were conducted on the LPA and DKR-1000 radio telescopes of the Lebedev Physical Institute. The giant pulses were analyzed using specialized software for calculating the magnitude of the scattering τ sc , signal-to-noise ratio, and other required parameters by modeling the propagation of a pulse in the scattering interstellar medium. Three pronounced sharp increases in the scattering were recorded in 2002–2010. Analysis of the dependence between the variations of the scattering and dispersion measure (data of Jodrell Bank Observatory) shows a strong correlation at all frequencies, ≈0.9. During periods of anomalous increase in scattering and the dispersion measure, the index γ in the frequency dependence of the scattering in the Crab Nebula, τ sc ( ν ) ∝ ν − γ , was smaller than the generally accepted values γ = 4.0 for a Gaussian and γ = 4.4 for a Kolmogorov distribution. This difference in combination with the piece-wise power-law spectrum may be due to the presence of a dense plasma structure with developed Langmuir turbulence in the nebula, along the pulsar’s line of sight. The magnetic field in the Crab Nebula estimated from measurements of the rotation measure toward the pulsar is 100 µG.

One of the linear antenna array versions consisting of four log-periodical (60-150) MHz antennas is considered as an array module of 4/spl times/4 elements. This module is intended to be a component of new meter wave radio telescope.

Practical and theoretical aspects of applying digital techniques to temporal beam shaping and signal processing in a meter-wave radio telescope are discussed. At present, digital signal processing (DSP) techniques are receiving primary attention in the design of new radio telescopes. The implementation of these techniques allows for more reliable and flexible systems to be created. The value of systems using DSP would particularly grow in connection with rough and unpredictable interference environments at radio telescope sites. A new 60-150 MHz meter-wave radio telescope under development is expected to provide simultaneous monitoring in several directions (2-3 beams), continuous tracking of investigated objects, signal reception and recording across several frequency ranges. The report discusses the issues of practically implementing DSP techniques in beam shaping, multibeam reception and in the analysis of radio telescope signals. The technique, circuit and program solutions will be fine-tuned using an existing PRAO DKR-1000 LPI radio telescope.

The second 16-beam far field pattern has been realized in BSA FIAN radiotelescope at the Pushchino Radio Astronomy Observatory. At present it is possible to perform simultaneous observations of cosmic radio sources for two scientific programs.

The radiotelescope BSA FIAN, constructed in 1974 in Pushchino Radio Astronomy of Astrospace centre of Physical institute of Russian Academy of Science (PRAO ASC LPI), is one of the most sensitive tools in the meter wave range. In 1998 the radiotelescope was reconstructed to be interference free, working in range 109-113 MHz. The dipoles, feed lines and pattern forming system were changed. The matrix for forming the 16 beam pattern is presented. This matrix is constructed from coaxial hybrid rings.

The characteristics of the “burst” (B) mode and “quiescent” (Q) mode pulse sequences–long known from studies at or below 103 MHz–are identified at 430 MHz for the first time. An 18-minute, Polarimetrie observation begins with a long Bmode sequence, which has a higher average intensity, regular drifting subpulses, and a preponderance of primary polarisationmode radiation. An abrupt transition to a Q-mode sequence is then marked by a) weaker average intensity, but occasional very bright individual subpulses, b) a complete cessation of drifting subpulses, with disorganized subpulses now being emitted over a much wider longitude interval, and c) near parity between the primary and secondary polarisation modes, resulting in pronounced depolarisation, both of individual pulses and the average profile.

A catalogue of integrated pulse profiles of 56 pulsars with observations at 102, 230, 408, 610, 1400, 4700, and 10500 MHz is presented. The profiles are aligned in time (phase) so that direct comparisons of changes in the profile shape and component composition can be made. Smearing due to interstellar scattering at low frequencies for pulsars with large dispersion measures was removed by means of a special "descattering': method (Kuzmin & Izvekova 1993).Most pulsars show good alignment over the whole frequency range 0.1 to 10.5 GHz, if the dispersion measure is corrected slightly in comparison to the published value. We confirm a non-dispersive time shift of the integrated profile for PSR 0809+74 as presented by Bartel et al. (1981), Davies et al. (1984), and Kuzmin et al. (1986).This paper presents the data in form of a catalogue of time aligned profiles. A detailed analysis of the change of pulse structure with frequency by means of a decomposition of the average pulse shape into gaussian components will be presented in a forthcoming paper.

This paper presents the results of the measurements of linear polarization characteristics of individual pulses at frequencies 40, 60 and 103 MHz for 10 strong pulsars. We have measured total intensity, linear polarization percentage and angle along the pulse window and obtained distribution displays for these data. Two orthogonal polarization modes are common features in the radiation of pulsars at low frequency. The energy ratio of these two modes can change significantly between different frequencies. The linear polarisation percentage has a general tendency to increase at low frequencies, but by very different factors for different components of the integrated intensity profile. The relationship between the polarization properties of PSR 0943+10 and its mode changing behaviour was studied. It is shown that the energy ratio and the frequency of occurence of two polarization modes change simultaneously with changes in the integrated intensity profile.

Pulsar 0943+10 demonstrates very obviously that the mode switching phenomenon includes simultaneous and dramatic alterations of all principal properties of radioemission, i.e. intensity, polarization (both linear and circular) and drifting behaviour of individual pulses over a broad frequency range. On the basis of observations of PSR 0943+10 at the frequencies 40 and 430 MHz, a complete scenario of the transition process between two modes of radiation has been revealed. The ''pre-switching transition process'' is found which manifests itself as attenuation of the pulse intensity of the current mode during hundreds of the pulse periods preceding a switch.

Observations of the pulsar PSR 0943+10 at 40 MHz (Pushchino, Russia) and 430 MHz (Arecibo, USA) have revealed a process that is a precursor to bursts of either of the two modes of radio emission of the pulsar pulses. In PSR 0943+10, a new mode is preceded by a gradual decrease in the intensity of the pulses, which gives way to a rapid decay one minute before a sharp switch from one mode to the other and which lasts for some time after this event. Variations in the intensity of the pulsar radio emission during the mode switching appear to be caused by the relaxation of a hot spot on the surface of the neutron star.

We performed the multifrequency time aligned measurements and the component structure analysis of the integrated profile of PSR 0329+54 in frequency range from 0.1 to 10 GHz. The result is that a commonly adopted five-component structure of the integrated profile does not provide a good match to the observed profiles. Only a six-component structure fits observations well. This result calls into question the validity of the two conal and core zones emission model. We suggest that the emission region inside of the cone of the open magnetic field lines represents a mosaic bunch of the discrete outflows of relativistic charges along magnetic field lines, injected by mosaic group of localized sparks in the polar cap. Our suggestion is based on the Rutherman and Sutherland belief that the polar gap discharges through a group of localized sparks, spaced at distances nearly equal to the height of the polar gap.Mode changing may be produced by the change of an activity of some sparks pattern without rearranging the structure of the emission region.

The relation between subpulses and the total pulse intensity of four pulsars is found from observations at frequencies from 30 to 1412 MHz. The subpulses constitute a distinct component of emission, with an appreciably different distribution of sources of emission.

A method of compensating the pulse profiles of pulsars for distortion by interstellar scattering, and restoration of their original shape, width and time position, is proposed. Its validity is investigated for the simplest form of scattering, corresponding to a thin screen. As a practical realization, low-frequency profiles of the pulses of PSR 0531 + 21 and 0136 + 57 are obtained.