In order to attract students to the radio universe, we have constructed a three-element radio interferometer in the National Youth Space Center, Goheung, Korea. It consists of three 1.8 m off-axis parabola antennas with driving systems, sideband separation receivers operating in 12 GHz, a narrow band digitizer, and correlation software. We have used as many commercial products as possible to reduce development costs. The maximum separation of 20 m gives an angular resolution of ∼4′, and the shortest baseline of 3.8 m prevents a serious missing flux. Fringes are detected for several radio sources, including the sun and Cas A. After a rough relative calibration, we have derived visibilities for the sun, whose amplitudes are decreasing for longer baselines. We have made a solar image using the visibility amplitudes and closure phases, referring to the 17 GHz image by Nobeyama Radioheliograph. Developing a flexible real-time correlator seems most crucial if this kind of the system is to be used for more rigorous scientific studies.

Introduction
Development of the Array
    Array Geometry and Antennas
    Antenna Driving and Control System
    Receivers
    Data Taking and Software Cross-Correlation
Test Observations
    Measurements of System Temperatures
    Single Dish Observations of Sun
    Fringe Detection 
Interferometric Observations
    The uv Coverage
    Calibration
    Derivation of Visibility
Imaging 
    Solar Disk
    Bright Spots
Discussion and Conclusions 
Acknowledgments
References

• Jeongwhan Han(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea)
• Sang-Eun Jung(National Youth Space Center, Goheung, Jeollanam-do 59567, Republic of Korea)
• Bangwon Lee(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Inwoo Han(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Biho Jang(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Yong-Sun Park(Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea, SNU Astronomy Research Center, Seoul National University, Seoul 08826, Republic of Korea) Corresponding author