In the amateur radio astronomy community, the “biggest” horn antennas for 1420 MHz hydrogen line detection typically follow the design principles of historical and specialized academic projects, balancing size with…
These may be debated by other builders……note I haven’t built this sized horn so cannot demonstrate its effectiveness – rather, this is my attempt to calculate the dimensions needed. https://www.astronomy.me.uk/wp-content/uploads/2026/01/Optimal-dimensions-of-3m-H-Line-Aperture-Horn-Antenna.pdf
https://www.astronomy.me.uk/wp-content/uploads/2026/01/Notes-on-SETI-style-Horn-of-Plenty-horn-antenna-tuned-to-H-Line.pdf
From SETI League on building Horn of Plenty: https://www.astronomy.me.uk/wp-content/uploads/2026/01/10629-scaled.jpg https://www.astronomy.me.uk/wp-content/uploads/2026/01/Building-SETI-Horn-of-Plenty2003.docx SETI League Feedhorn Excel Spreadsheet Calculator: https://www.astronomy.me.uk/wp-content/uploads/2026/01/SETI-League-Feedhorn-Analysis-Excel-Calulator.xls Design for my own Horn of Plenty using diagrams and photos from SETI…
This calculator calculates the optimal dimensions of a Pyramidal Horn. Click on link below to see examples of calculation for hydrogen line radio observing (1420 MHz): https://www.astronomy.me.uk/wp-content/uploads/2025/12/Pyramidal-Horn-Calculator-with-examples-091225.pdf
Below is a complete, practical guide to designing and building a 1-metre-aperture horn antenna for 1420.405 MHz suitable for hydrogen-line work. I’ll give you dimensions, materials, flare angles, feed options,…
Here’s a practical WR waveguide reference table showing common WR numbers, their frequency range, and corresponding free-space wavelengths, and including a selection of sizes useful for radio astronomy and microwave…
Links to two useful calculators below (I have nothing to do with these websites): https://3g-aerial.biz/en/online-calculations/antenna-calculations/cantenna-online-calculator https://www.everythingrf.com/rf-calculators/pyramidal-horn-antenna-gain-calculator
Good questions. First, to be clear — by “convert … to a full waveguide” I assume you mean: you have a (a waveguide‑to‑coax adapter) and you want to use it…
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