A High Resolution Radio Telescope for Use at 3.5 M

A pencil-beam radio telescope of the cross type is described; it has a beamwidth of 49 minutes of arc and a sensitivity which approaches, under ideal conditions, 2×10-26 W m-2 (cps)-1, that is, about 1/10,000 the flux density of the strongest radio source. To speed the collection of information the beam may be scanned, presenting information on five separate declinations quasi-simultaneously. Although it is intended primarily as a survey instrument, strong radio sources may be located with high accuracy; the probable errors in the measured positions of the stronger identified sources average less than a 1-foot arc. Methods of calibrating the flux density and temperature scales are described and some examples are given of the use of the radio telescope. The theory of operation and some of the design factors are discussed and it is concluded that, for a given size of antenna and the best snr on a typical radio source, the wavelength is rather well defined. This optimum generally lies in the range 2 m to 4 m, depending on details of the receiver and antenna design; other factors, however, play an important part in the choice of wavelength.