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Since 2011 Ventspils International Radio Astronomy Centre has been involvedin the large scale infrastructure project which allowed significant speeding-upof the upgrading activities related to radio telescopes RT-32 and RT-16 as toits fitting with appropriate VLBI receiving and recording equipment. Radiotelescopes were instrumented with new state-of-art broadband cryogenicreceivers for frequency range of 4.5 - 8.8 GHz developed and installed bycompany Tecnologias de Telecomunicaciones e Informacion. In this paperarchitecture of receiving system as well as significance and working principlesof key subsystems are described. The receiver is formed by a cooled RFsubsystem and a room temperature IF subsystem. The RF and IF subsystems aredesigned to process two C and X band signals (LCP and RCP) in parallel.Normally, during observations, the measured vacuum level in the receivers dewaris from 10e-6 to 10e-8 mbar and the temperature inside dewar is at level of 14K at second stage, 20 K at polarizer and 46 K at the first stage. Since October2015 radio telescope RT-32 with new receiver system took part in severalsuccessful international VLBI sessions. During preparation for VLBIobservations preliminary aperture efficiency, system temperature and beampattern measurements were carried out to evaluate RT-32 performance after thestations renovation that besides the receiver also included repairing of themain reflector. Performance parameters were derived with the help of switchingnoise diode and on-off observations of calibration sources with known fluxdensity at various elevations. First results measured at 4836 MHz aresummarized in this manuscript.

Broadband receiving systems for 4.58-8.8 GHz radio astronomical observations at Irbene radio telescopes RT-32 and RT-16