A Glider pilot on downwind to 4S2 non-towered airport reported a NMAC with another aircraft entering the pattern.

Narrative

While giving instruction we experienced a close encounter with another aircraft. The situation was as follows. Winds were light out of the east. Traffic was an Aircraft Y reporting about 5 miles northwest; planning Runway 07. I was on a 45 for Runway 07 so I reported my position and intentions. Another aircraft responded that he was inbound for 25 at Hood River. His transmission was somewhat garbled; somewhat masked by ambient noise in the glider. Our transmissions have frequently been reported to be unreadable also. As we were flying downwind we observed a shadow on the ground coming directly at us. We both looked up and observed an Aircraft Z pass directly over us; possibly 100 feet above. I asked Aircraft Z if he had seen the glider as I was turning base. At this point I was concerned about a runway confrontation. The response I got indicated he had not seen us; but he did break off his approach to give way to us.Opposite direction traffic is a hazard that always exists at uncontrolled airports; especially when winds are light. Hood River Airport is especially susceptible; with glider traffic designated to use right hand traffic and powered aircraft to use standard left hand patterns. Contributing factors in this incident were the facts that both a glider and an Aircraft Z have exceptionally thin profiles when viewed head on and an aircraft on collision course has no apparent relative motion to the pilots. To mitigate the possibility of an unlucky outcome to a future similar event; I am proposing that glider traffic for 07 enter downwind on a 45; near midfield at an altitude of 800 ft. This is consistent with the landing pattern depicted in Appendix A of the HRS operations manual. The opposite direction powered aircraft should be doing the same at 1;000 ft; beginning descent at midfield. Also CTAF communication between aircraft is essential for safe operation. Although not required; HRS should prioritize clear communication equipment in all gliders; especially commercially operated gliders. The opportunity for conflict certainly is more likely to occur during light east wind conditions when some aircraft are landing on 07 into the wind and some aircraft opt to land on 25 with an uphill gradient and toward facilities. But; as always; vigilance is required when landing on 25. Runway 07 is still advertised as the preferred noise abatement runway.