Link below to URL of webpage with such a calculator: https://www.everythingrf.com/rf-calculators/pyramidal-horn-antenna-gain-calculator
Here’s a side-by-side comparison of horn-antenna dimensions for hydrogen-line (≈1420 MHz, λ ≈ 21 cm) observation from SETI League / astronomy.me.uk recommendations and the academic designs referenced in the Harvard/McMaster…
Short answer first, then the nuance. TL;DR (rule-of-thumb) For 1420 MHz hydrogen-line pyramidal horns: That’s why almost all serious 21 cm horns cluster around 15–25°. What “problems” actually appear —…
Hi Andy, You recently asked a question on the SARA forum “I notice that the SETI Horn of Plenty is a smaller version of the original Ewen Horn that first…
Same frequency, physically bigger horn — not frequency scaling.This is where horns stop being “just scaled” and start being designed. Short answer first:You increase the aperture size, but you do…
Short answer: it scales linearly with wavelength.Longer answer (the bit you actually care about 🙂): For a hydrogen-line horn (≈1420 MHz, λ ≈ 21 cm), the flare geometry is set…
Following is result of asking ChatGPT the above question 27/1/2026!!!! Here’s a source that actually describes the original SETI Horn of Plenty antenna design and its dimensions: 🔗 SETI League…
Excellent — I’ll go through all four, keeping it practical and tied to 1420.405 MHz H-line work with WR-650. 1. Field patterns in WR-650 at 1420 MHz For the dominant…
Short answer: because different people are talking about different operating regions of the same waveguide, and some descriptions quietly assume single-mode, low-loss, well-matched operation rather than mere propagation. Here’s the…
https://www.astronomy.me.uk/wp-content/uploads/2026/01/Plan-Measurements-for-LRO-Horn-of-Plenty-140126.pdf
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