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 —…
Just to finish off my posts on sudden ionospheric disturbances, there were two massive complex ones closely following on from each other today, representing a series of solar flares hitting…
Interests me how different stations show quite different traces. Here is mine (Lichfield Radio Observatory www.astronomy.me.uk) from 21/1/2026: It shows a very impressive SID at about 1pm. My goto website…
Strangely narrow SID on 26/1/2026 associated with C-class flare: From Lichfield Radio Observatory (my observatory in UK): Compare to SID Monitoring Station (https://sidstation.loudet.org/data-en.xhtml) – an excellent source of high quality…
Admin