Relative power response P(Θ) of radio telescopes with different aperture diameters. Θ is the angular distance between the source and the pointing (maximum response) direction of the antenna. The central wavelength (λ = 18 cm) was used to estimate the FWHM of the primary beam. The primary beam correction values for J2229+0114 and J2228+0110 (at ) are also shown (see the text and Table 3 for details). The WSRT in phased array mode has a collecting area equivalent to that of a single 90-m antenna, but its high angular resolution is determined by the maximum baseline length between the elements of the array (nearly 3 km).