How do switch blocks and selector blocks in GNU Radio work?
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These two get mixed up all the time in GNU Radio because they sound similar but solve slightly different problems. I’ll explain them intuitively first, then a bit more technically,…
February 2026
Pyramidal Horn Antenna Gain Calculator
Link below to URL of webpage with such a calculator: https://www.everythingrf.com/rf-calculators/pyramidal-horn-antenna-gain-calculator
What thickness of monopole probe in cantenna matches 50 ohm impedance of hydrogen line radio telescope?
There isn’t a single magic thickness that by itself gives 50 Ω — but in practice, for standard rectangular waveguide probe feeds, there is a very reliable working range that…
How does thickness of monopole probe in a waveguide affect impedance?
Short answer: a thicker monopole probe looks electrically “fatter,” which lowers its impedance and broadens the match. Longer, more intuitive version 👇 What’s going on physically A monopole probe in…
How to calculate F/D ratio of radio dish?
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…
How do I find F and D if I don’t know them? (Focal length and diameter of a radio dish)
Short, honest answer first: you can’t get absolute F or D from the dish shape alone without at least one real measurement. A parabola has no inherent scale. But —…
What is design working temperature of Nooelec NESDR Smartee software defined radio?
The (Nooelec NESDR Smartee) USB SDR dongle does not have a publicly listed official “design or operating temperature range” in its published specifications from Nooelec. The manufacturer datasheets and product…
I am looking for a GNU Radio flowgraph on Github or elsewhere that shows me how to incorporate ability to choose between SDRs whilst running the program.
Here are some open-source GNU Radio flowgraphs / projects on GitHub that you can study or adapt when you want to choose between different SDR hardware sources (e.g., RTL-SDR, USRP,…
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 —…