6 ms·
Radios, how do they work? (2024)
- deleted 11mo ago[deleted]
- giuliomagnifico 11mo agoThe article is interesting but some images have Error 400 so I can’t see them.
- mrasong 11mo agoProbably just a network hiccup. I ran into the same thing earlier, but it worked fine after a couple refreshes.
- tomhow 11mo agoPreviously: Radios, how do they work? - https://news.ycombinator.com/item?id=39813679 https://news.ycombinator.com/item?id=39813679 - March 2024 (109 comments)
- psyclobe 11mo agoCool article; I’m still baffled though.
- tiniuclx 11mo agoI've been studying for my amateur radio license recently, and this article is a great introduction to the basics. But really, if you want to get your hands dirty with some practical electronics, and also want to be able to communicate without relying much on nearby infrastructure, amateur radio is a great hobby.
- DrAwdeOccarim 11mo agoDo yourself a favor and study for both your technician and general at the same time (I’m assuming you live in the US). HF is exponentially more fun than just VHF/UHF.
- i_am_a_peasant 11mo agoit’s stuff like this that make me wish i lived in the US. i have to memorise a long questionnaire in german if i want to get my license
- GJim 11mo agoYou can take your licence exam in any CEPT country and swap it (i.e. that countries licence) for a German one under reciprocal licencing agreements. https://www.cept.org/ecc/topics/radio-amateurs https://www.cept.org/ecc/topics/radio-amateurs
- hrimfaxi 11mo agoYou have to memorize a long questionnaire in the US (though in English) to get it there, too.
- ux266478 11mo agoOnly the entry level license (Technician in the US, covering UHF/VHF) is substantially different from the German one, and it's also much more restricted. Germany in general is a much better country for radio, especially if you wanted to ever do high power broadcasting. I think the one perk to the US is that the FCC has basically stopped caring about all but the most important frequencies. This makes HF particularly fun, since HF pirate radios are often the best listening stations in the entire RF spectrum. I have no idea what that's like in Germany, but I would imagine given the general ordnung culture and veneration of rules, German hams are much less tolerant of flagrantly unauthorized broadcast stations and your regulatory bodies are more proactive in shutting them down.
- know-how 11mo ago[dead]
- gwbennett 11mo agoGreat advice!
- tzs 11mo agoTake a look at Extra too. You may find that it actually isn't much harder than General. The Extra exam is 50 multiple choice questions broken down by category as follows: 6 Commission Rules 5 Operating Procedures 3 Radio Wave Propagation 5 Amateur Practices 4 Electrical Principles 6 Circuit Components 6 Practical Circuits 3 Signals and Emissions 8 Antennas and Transmission Lines 4 Safety You need to get 37+ correct to pass. Another way to think of that is you can get up to 13 wrong and still pass. Within each category there are subcategories. "Antennas and Transmission Lines" for example has 8 subcategories. The 8 questions in "Antennas and Transmission Lines" are one from each of those subcategories. The question pools for these subcategories each have 10-14 questions. If you compare to the closest corresponding categories/subcategories from the General and Technician exam you'll probably find that there are a few cases. 1. The Extra is just more of the same. It's not harder per se. "Commission Rules" for example. 2. The Extra goes goes deeper and also adds new material that is more advanced. 3. The Extra is in new territory. If you get to the point where the Technician and General are going to no problem, then you will probably have no trouble getting to the point where case #1 is also no problem, and case #2 is also well in hand. It is #3 where you might have trouble. But remember that you can get 13 wrong and still pass! Pick say 10 subcategories that are in case #3 that look like they would be the hardest to get good at and just write them off. For example in "Antennas and Transmission Lines" you might decide that the "Smith chart" subcategory, which has a pool of 14 questions, would take a lot of time to get good at. So skip it. That's 14 less potential questions you have to be prepared to answer, leaving more time to study for things in class #2 and the class #3 things that look most doable. It doesn't cost extra to take the Extra test at the same session that you take the Technician and General tests, and there is no penalty for failing, so might as well go for it.
- gtsnexp 11mo agoThis reminds me of a beautiful book written by Paul Nahin, 'The Science of Radio'.
- dd_xplore 11mo agoTo get an idea about radios, I made a crystal radio when I was in 7th grade, I only had few components. The only component I had difficulty in getting was the crystal oscillator (I was living in a rural town). It was mind blowing when I first heard the audio through IEMs ! It felt magical that this contraption was working without any battery source.
- immibis 11mo agoThe crystal radios I know don't have crystal oscillators - the word "crystal" refers to the diode.
- gtsnexp 11mo agohttps://www.youtube.com/watch?v=-GxL13rid1w https://www.youtube.com/watch?v=-GxL13rid1w
- kragen 11mo agoThis is a video about the diode, in this case a Schottky diode made with a coil of copper wire filed to a fine point touching a piece of galena sitting loose in a bottlecap found by the side of the road. The video is notable for demonstrating the original "breadboard" technique, where you connect your wires and components by clamping them to a wooden board with the head of a wood screw. The book I learned the technique from recommended using a dished washer under the head of the screw so that the screw head doesn't push the wires sideways as you tighten it.
- dd_xplore 11mo agoPerhaps I'm getting confused cuz this was long back. But I think it was a oscillator for sure...
- pkolaczk 11mo agoYou can use a germanium diode or even Shottky now instead of a “crystal”. Such a simple radio can be a gateway drug to a very complex and deep hobby. In my case it went like that: 1. Built a simple radio 2. Could hardly hear anything, need to add an amplifier to it 3. Now it’s better but captures a lot of noise 4. Design a filter to select just that one station 5. Now I want to listen to more stations. 6. Ugh, you can’t design a good filter with variable frequency. Enter the superheterodyne world. 7. Now finally got something that resembles a tunable AM radio, but it kinda whistles / hums a lot. Ah, so the mirror image is a real thing?! 8. Need a higher IF to be able to better reject the image before the mixer. Ok, let’s make a double conversion superhet then. 9. Buy a set of ceramic filters and play with them to get the best selectivity. 10. Try to add more amplification only to learn if you go too far you get an oscillator instead of an amplifier. 11. The sound level is not stable. Add AGC. 12. Pick up some stations from 5000+ km away. Nice. But there is some weird distortion. Oh, I’ve been a culprit of frequency selective fading… Fast forward and now I’m building a PLL synchronized AM product demodulator with a squaring loop for carrier recovery. Fun. Lot of fun! Wholeheartedly recommend!
- hshdhdhehd 11mo agoNever thought about the AM bandwidth thing before that is interesting and seems obvious now (from Fourier Transform point of view)
- drmpeg 11mo agoHere's a video of AM modulation. SDR transmitter (running GNU Radio) connected to an SDR receiver. https://www.youtube.com/watch?v=9LsJn0CyyZI https://www.youtube.com/watch?v=9LsJn0CyyZI
- deleted 11mo ago[deleted]
- randyrand 11mo agoneeds more pictures!
- Liftyee 11mo agoI've been learning about radios for a while, and this article explained one of the key questions I had: why can't you turn on and off some single frequency waveform faster to transmit data faster? (answer: changing amplitude messes with the spectrum and makes it no longer a single frequency...) I tend to prefer these visual and intuitive explanations to the mathematically based ones usually given in lectures. The "open capacitor" example was something I hadn't thought of before.
- tigereyeTO 11mo ago> In today’s article, I’m hoping to provide an introduction to radio that’s free of ham jargon and advanced math …(scroll)… > The identity for cos(α + β) can be trivially extended to cos(α - β), because subtraction is the same as adding a negative number: …(scroll)… > From the formula we derived earlier on, the result of this multiplication necessarily indistinguishable from the superposition of two symmetrical sinusoidal transmissions offset from a by ± b, so AM signals take up bandwidth just the same as any other modulation scheme.
- foobarian 11mo agoTo be fair, they did qualify it as "advanced" math :-)
- mholt 11mo agoI got my amateur radio license last year, and this is precisely why I haven't been able to do much with it: seemingly all the guides, even the license study materials, use vocabulary I'm not familiar with. I have two CS degrees and a solid foundation in math, but I can't understand how radios work because of vocabulary more than the math. My uncle who's been building his own radios for over 60 years, tried to explain to me how antennas work, and even to him it comes down to "black magic". I'm told the way they work is not really intuitive, so you just have to math it out. Maybe I should have gotten an EE degree.
- esseph 11mo agoIt gets crazier when you start talking about things like a Tarana BN. The amount of processing in them is pretty insane. But yeah, black magic is right!
- hedgehog 11mo agoEven just the theory is kind of mind expanding. I've done a little signal processing and ideas like "negative frequency" sound absurd up front and then seem reasonable once you've worked with them.
- _whiteCaps_ 11mo ago
- supportengineer 11mo agoEDIT: I am offended that you guys think my awesome explanation is from GenAI. Imagine a circuit. Like a flashlight. The electrons flow from the battery to the lightbulb and back. It’s like a race track. They proceed in an orderly fashion. There are some other electrical components. If you hook them up in just the right way, you get something called an LRC circuit. The electrons don’t flow in an orderly way now. They go back-and-forth. In spurts and fits. You’re making them wiggle. There are some very nice equations that allow you to specify exactly how much and how fast the wiggling is. One cool thing about a circuit with wiggling electrons is that if you put some wires close by those electrons will also start wiggling. This is called radio.
- deleted 11mo ago[deleted]
- neduma 11mo agoI was listening to story of QualComm in Acquired podcast. This is highly related.
- bdcravens 11mo agoMy grandfather, when he was a boy in the 1910s or 1920s built a radio out of a round oatmeal box, copper wire, and a crystal. I never saw the original, but he built a replica of it (featured in a book in the 1970s) that I saw as a child. https://sg30p0.familysearch.org/service/records/storage/dascloud/patron/v2/TH-7771-104446-17278-18/dist.jpg https://sg30p0.familysearch.org/service/records/storage/dasc...
- tonymet 11mo agoThis is a great review, but don't let theory interfere with practice. There's an art and feel to radio and antenna building. I've built antennas with scrap wire and baluns without double checking . Just a rough length of wire tweaked until you hear someone. The theory seems overly complex (because it is). but for practical radio you can tune up nearly anything and chat -- and be way more productive with it. Imagine obsessing over the mechanics of baseball or fishing without ever tossing a ball or casting a reel.
- deleted 11mo ago[deleted]
- mikewarot 11mo agoIf you dig deeper, you end up with I/Q signals. If you take the input from the antenna and delay it by 90 degrees, you then have something which can have a positive or even negative frequency. Using multiplication of complex terms, you can add or subtract frequencies without generating unwanted images. You could also use signals from 2 antennas 90 degrees apart to get I and Q. This gives you the added ability in that signals from one side has a negative frequency. It's some really useful stuff.