tags : Electronics, Hardware stuff
resources
- M17 (amateur radio) - Wikipedia
- Software-defined (Internet) radio with Liquidsoap (2023) | Hacker News
- https://www.clearskyinstitute.com/ham/HamClock/
- Why does FM sound better than AM? | Hacker News
- How ham radio endures | Hacker News
- Show HN: RF Hunter – Find hidden cameras and other devices | Hacker News
- I discovered mysterious hidden signals on a public radio channel (2013) [video] | Hacker News
FAQ
Radio in everyday life
- NFC (eg. Apple Pay) is a radio, range a few cm. Bluetooth is a radio, a few meters. WiFi is several radio systems, range tens of meters. Cell phone is several radio systems, range up to kilometers. GPS (and rival systems) range up to thousands of kilometers.
- NFC is not really a radio. Basically it uses a loosely copled transformer. Works much closer than 1 wavelength and only magnetic field matters.
- Good point, NFC is described as operating in a particular RF band but not through radio waves:
Essence
- “Essence of radio is very simple … radio station broadcasts a high power RF signal into which some human listenable audio (your favorite singer’s song) is mixed … so the radio station propagates this RF signal modulated by the song being played … across town at your house your radio synthesizes an RF signal identical to that broadcast from the radio station … your radio amplifies the result of combining its local RF signal together with the received RF signal from the radio station … this combining will add together both RF signals it will also subtract both … when it subtracts ( wave interference ) the result is the difference between the radio station modulated RF signal and your radio RF signal (both at identical frequencies) which leaves you with just the song”
How much to know for hobbists?
Radio communications play a key role in modern electronics, but to a hobbyist, the underlying theory is hard to parse.”
I don’t believe radiocommunications and the electronics of radio is hard to understand—at least that’s so at a level where a hobbyist can gain enjoyment from the subject.
I say that as someone who obtained a radio amateur’s license in junior highschool at age 15.
Yes, radio engineering and its physics does get very complicated at the high end, and for a good understanding one requires advanced math including partial differential equations such Maxwell’s equations and their SR/Special Relativity extensions, and beyond that one needs to understand the physics of electrodynamics and that requires knowledge of quantum mechanics including QFT (Quantum Field Theory), which is top-echalon physics and close to as complex as physics gets.
However, the hobbyist doesn’t need to know an iota of that advanced complex stuff to enjoy radio as a hobby. Absolutely none of it.
All that he/she needs to know are very basic principles such as how antennas receive and radiate signals, how radio signals are amplified and detected, and later on how signals are mixed, multiplied and hetrodyned, and how radio transmitters and receivers work—even the principles behind how the common superhetrodyne receiver works is pretty standard knowledge for a radio hobbyist.
Back when I was learning about radio I doubt very much if an article would have been written in the tone of this story, especially so one that implied that to understand the subject could be difficult even at a hobby level. Why, you may ask? Well back then, if anyone had a hobby interest in electricity and electronics then essentially the only outlet for their interest was radio and perhaps television, as the other branches of electronics would not have been as readily accessible to hobbyists.
Nowadays, that’s changed, there’s much more to keep a hobbyist’s interests such as programming, computers, computer games, and other electronics not based on radio technology—digital electronics for instance, so knowledge about radio tech and radiocommunications theory have become much less commonplace having been diluted amongst all these competing interests. Obviously, the knowledge is still out there but it’s more widely dissipated and not as easily accessible in the practical sense, especially so for hobbyists of a young age.
When radio was essentially all that there was around there were many more elementary books on radio available for younger readers and these increased in complexity as the hobbyist gained practical experience. For instance, when I first became interested in radio my first introduction to the subject—like most others—was building crystal set radios, and from there we advanced to incorporating tubes and transistors into our more advanced designs. For beginners, hands-on practical books such as how to build crystal sets which included many different designs were commonly available.
(Back then, a well known author of books on crystal sets and basic radio was Bernard B. Babani, an unforgettable name if ever there was one. His books are still available but you’d never know to look for them unless told about them.)
Today, many have never heard of crystal sets let alone their ‘cats’ whisker’ detectors, so when they become interested in the subject they’re thrown in at the deep end. And not having the basics already under their belts, the more advanced radio theory comes as a bit of a shock.
5G
- Glass Antenna Turns windows into 5G Base Stations | Hacker News
- GitHub - SysSec-KAIST/LTESniffer: An Open-source LTE Downlink/Uplink Eavesdropper