A new 6cm receiver has just been mounted on the VLBI parabolic antenna of the Medicina station, improving the sensitivity of almost a factor of two with respect to the old receiver.

It was designed in order to show very good performances in a large bandwidth and with the best performance in term of temperature noise and antenna gain (SEFD). It uses a dual flare corrugated horn, a circular waveguide irises polarizer and a square waveguide omt. The crosspolarization performance has been optimized in the central part of the band, the VLBI band.

A noise calibration injection is provided via a square waveguide directional coupler.

Both polarizer and omt are cryogenically cooled together with the LNAs.

Standard parameters of the 5 GHz receiver (*400 MHz IF filter)

To shift the IF standard band inside the RF band by Δν, the OL frequency must be changed (within the range listed in the table) according to the following :

Receiver noise temperature

5 GHz receiver scheme

Receiver mounted

Conversions scheme

5-7 GHz converter