The hardware is fairly straightforward. Two antennas are available, an experimental interferometer for measuring arrival angles and a steerable yagi array for most other observations. The SSB receiver converts the 216.98 Mhz signal down to audio tones, where a sound card (similar to SoundBlaster) is used to digitize it for later DSP processing on the computer. The homebrew calibration standard provides both RF and time signals to permit highly accurate measurements of doppler and time of fence crossing. The HF receiver is used to provide WWV time signals for setting the time and measuring the drift of the calibration standard.