Here are some good internet resources — guides, tutorials, and reference material specifically useful for getting into hydrogen-line (21 cm, ~1420

A power user is someone who uses a product, system, or piece of software far beyond basic or casual use,

Astronomers determine a star’s age using starquakes through a technique called asteroseismology. The basic idea is that a star’s internal structure changes in

Key messages from above table: The probe length does not change with cantenna diameter at the same design frequency. The

The following calculations were developed with help of the calculator at https://3g-aerial.biz/en/online-calculations/antenna-calculations/cantenna-online-calculator

A ZIP file of the entire set of calculators from the SETI League website 1/1/2026. https://www.astronomy.me.uk/wp-content/uploads/2026/01/SETI-League-Excel-Spreadsheet-Templates-Calculators.zip

These may be debated by other builders……note I haven’t built this sized horn so cannot demonstrate its effectiveness – rather,

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

https://www.astronomy.me.uk/wp-content/uploads/2025/12/Calculating-Cantenna-Dimensions-for-H-Line-Meeting-050126-DRAFT-301225@2330.pdf https://www.astronomy.me.uk/wp-content/uploads/2025/12/Calculating-Cantenna-Dimensions-for-H-Line-Meeting-050126-DRAFT-301225@2330.pptx