Investigation of the spatial distribution of plasma parameters has shown that a large diameter uniform plasma (over 160 mm) can be sustained over a broad pressure range (10 - 230 Pa) by a surface wave at 2.45 GHz. Optical emissions testify the existence of azimuthal modes of m = 4 at a pressure of 10 Pa and m = 6 at a pressure of 230 Pa. The electric field of the m = 4 mode, on which the plasma distribution strongly depends, has also been studied.