  Extraterrestrial communication signals are hypothesized to be present in an
extensive search space. Using principles of communication theory and system
design, methods are studied and implemented to reduce the signal search space,
while considering intentional transmitter detectability. The design and
observational work reported in this paper adds material to previous related
reports. (ref. arXiv:2105.03727, arXiv:2106.10168, arXiv:2202.12791,
arXiv:2203.10065). In the current work, a two-element radio interferometer
telescope and receiver algorithms are utilized to perform differential
angle-of-arrival and multi-bandwidth measurements of delta-t delta-f polarized
pulse pairs. The system enhances extraterrestrial signal detectability, while
reducing signal false positives caused by noise and radio frequency
interference. Statistical analysis utilizes a Right Ascension filter spanning
celestial coordinate ranges that include the previously determined anomalous
celestial direction: 5.25 +- 0.15 hr Right Ascension, -7.6 degrees +- 1 degree
Declination. Observations were conducted during a duration of 61 days,
comprising 244 hours of interferometer measurements.
