Abstract
As a continuation of a previous work by Park et al. (2006), we have developed a two-element radio interferometer that can measure both the phase and amplitude of a visibility function. Two small radio telescopes with diameters of 2.3 m are used as before, but this time an external reference oscillator is shared by the two telescopes so that the local oscillator frequencies are identical. We do not use a hardware correlator; instead we record signals from the two telescopes onto a PC and then perform software correlation. Complex visibilities are obtained toward the sun at ${\lambda}\;=\;21\;cm$, for 24 baselines with the use of the earth rotation and positional changes of one element, where the maximum baseline length projected onto UV plane is ${\sim}\;90{\lambda}$. As expected, the visibility amplitude decreases with the baseline length, while the phase is almost constant. The image obtained by the Fourier transformation of the visibility function nicely delineates the sun, which is barely resolved due to the limited baseline length. The experiment demonstrates that this system can be used as a "toy" interferometer at least for the education of (under)graduate students.