I. N. Bubnov

Digital Receivers for Low-Frequency Radio Telescopes UTR-2, URAN, GURT

This paper describes digital radio astronomical receivers used for decameter and meter wavelengthobservations. Since 1998, digital receivers performing on-the-°y dynamic spectrum calculations or wave-form data recording without data loss have been used at the UTR-2 radio telescope, the URAN VLBIsystem, and the GURT new generation radio telescope. Here, we detail these receivers developed foroperation in the strong interference environment that prevails in the decameter wavelength range. Datacollected with these receivers allowed us to discover numerous radio astronomical objects and phenomenaat low frequencies, a summary of which is also presented.

Using of pulsar spectra catalogue at frequencies below 80 MHz for astronomical calibration of phased antenna arrays

In this paper we show a possibility of applying the technique of radio astronomical calibration of antenna arrays of low-frequency radio telescopes using pulsar radio emission. A placement of two low-frequency radio telescopes UTR-2 and GURT at one observatory gives us a unique possibility of joint simultaneous observations in the same ionospheric conditions. In the paper results of B0809+74 pulsar observations are used to illustrate the proposed technique.

SNRs of two active antenna designs: Inverted V vs horizontal dipole

We present the results of numerical analysis of two design versions of active antenna which were considered for using in phased antenna array of GURT radio telescope at the stage of preliminary design. Both antenna versions are supplied with the same preamplifier but their dipole shapes differ. The first active antenna version has linear horizontal dipole, the second one — inverted V-dipole. The differences of input impedances, efficiencies, and mismatch coefficients of dipoles with preamplifier as well as the effect of these parameters on noise temperatures and SNR of antennas are analyzed in detail.

Diamond dipole active antenna

Advantages of the diamond dipole antenna as an active antenna are presented. Such an antenna is like an inverted bow-tie antenna, but the former has some advantages over the ordinary bow-tie antenna. It is shown that the diamond dipole antenna may be an effective element of a new antenna array for low-frequency radio astronomy as well as a communication antenna.

Variation of phasing system parameters of GURT active antenna subarray in a wide scan range

In the abstract the results of transfer coefficient calculations of active antenna subarray of GURT radio telescope for all possible scan directions are presented. Also these results are supplied by measurements of signal changing with beam switching at subarray of GURT radio telescope which prove the correctness of the computations. The presented results could be useful for designing of new active antenna arrays and interpreting data obtained at present antenna arrays.