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▸ Graphical User Interface for Chinese 16-channel USB-serial relay boards: This is a stand-alone python program that was developed as a receive antenna selector for the N2CEI 160m contest station. It can be readily adapted for other applications. Uses tkinter widgets and requires installation of pyserial and tk-tools. Has been shown to work on Linux and Windows. ▸ Propagation of 50 MHz radio waves in the E-layer: 537 kb pdf. This paper suggests that Faraday Rotation may help explain spotlight propagation that often accompanies sporadic-E openings. Data collected by Deacon et al reveal that horizontally polarized 50 MHz signals generally become elliptically polarized upon reflection from the E-layer. A real-time video from these authors reveals rapid Faraday Rotation on a 1270 km sporadic-E path from the horizontally-polarized OY6BEC beacon. When the ionosphere is in such a dynamic state, 15-second FT8 sequences are likely too long to obtain decodes. ▸ Is tropospheric ducting a myth?: 2.0 Mb pdf. These slides are from a presentation at the 2025 Central States VHF Conference. I was hospitalized and unable to attend, so this talk was given by Jim Duffey KK6MC. A deep-dive analysis can be found in the Proceedings paper (updated December 2025). ▸ High-Power, Fail-Safe Antenna Switch: link ▸ Antenna Modeling with xnec2c: link ▸ We communicate by ionspheric reflection -- not refraction: 2.1 Mb pdf. These slides are from a presentation given at the 2024 Central States VHF Conference. An accompanying paper was published in the Proceedings, but has several print errors that rendered some equations incorrectly. Key takeaways were corroborated later in 2024 in this talk from the US Naval Research Labs. ▸ Doppler shift on meteor scatter pings: 451 kb pdf ▸ Meteor scatter with very short pings: 460 kb pdf. An earlier version of this paper was published in the 2020 Southeastern VHF Society Technical Journal. ▸ FSK441 vs MSK144 for meteor scatter communication at 222 MHz was the subject of a short presentation at the Central States VHF Society Annual Meeting in 2022. ▸ Synchronization in FT8: 452 kb pdf This note is based on my attempt to reverse-engineer portions of the mostly undocumented Fortran open-source code. I did not have access to protocol design documentation and this paper has not been endorsed by the WSJT-X developers. This paper was presented at the 2019 TAPR Digital Communications Conference. A video recording of the talk is available on YouTube and at Ham Radio 2.0. ▸ GS23B Tetrode Amplifier for 144 MHz: link. ▸ Reflection from ionized meteor trails at 50 and 144 MHz: 83 kb pdf |