How to calculate F/D ratio of radio dish?
Admin
F/D is purely geometric. Once you know any two of diameter, focal length, or depth, you can calculate it. Definitions: D = dish diameterf = focal length (vertex to focus)d…
Radio Astronomy
How do the dimensions of the hydrogen line horn made by SETI League & listed on astronomy.me.uk compare to the ones in https://lweb.cfa.harvard.edu/~npatel/hornAntennaAASposterPDF2.pdf and https://www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/
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…
What is maximum flare angles of hydrogen line horn antennas before the antenna develops problems?
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 —…
Two successive massive complex SIDs today 1/2/2026, representing a sequence of multiple solar flares arriving at Earth
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…
Variable display of SIDs on SID monitors (Sudden Ionospheric Disturbances)
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 around midday
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…
My muon detector, and a number of other people’s around the world, has shown significant dip in muon detector on 20 January 2026. A CME hit the atmosphere of Earth on 19 January 2026. Are the two related?
Dip in Muons detected on the UKRAA PicoMuon detector at LRO 20/1/2026: Yes — they’re very likely related. Here’s why: 📡 What happened on 19–20 January 2026 🌍 How CMEs…
Scaling the SETI Horn of Plenty (Hydrogen Line Horn Antenna)
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…
If I want to make a bigger version of the SETI Horn of Plenty, still for 1420 MHz, how do I increase the dimensions?
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…
How does flared section of hydrogen line horn antenna scale with changes in wavelength measured?
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…