1J17B / 1Zh17B Miniature HF Pentode Tube Mil-Spec. The 1J17B / 1Zh17B (Cyrillic: 1Ж17Б) is a subminiature, battery-powered high-frequency (HF) pentode vacuum tube. Due to their surplus availability, military reliability, and unique physical format, 1j17B tubes are popular among DIY electronics hobbyists.