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Radios, how do they work? (2024)

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Re: Radios, how do they work? (2024)

#41

Post by ux266478 »

i_am_a_peasant wrote: post #17
DrAwdeOccarim wrote: post #16

Earlier quoted context omitted.

Do 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.

it’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

Only 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.

Re: Radios, how do they work? (2024)

#42

Post by kragen »

tigereyeTO wrote: post #24

> 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 sinus…

This is basic math, not advanced math. If you don't know it, don't worry, you can learn it pretty quickly. Maybe watch some 3Blue1Brown videos and do some textbook exercises and/or game programming. Git gud. There is no royal road to radio modulation.

I learned that subtraction was the same as adding a negative number sometime around second grade, and I learned (then forgot) the trigonometric angle-sum identities in tenth grade. And that was even with the handicap of having to attend school in the US.

And, just above the text you're complaining about, he even provides a straightforward geometric proof of the angle-sum identity! So you don't even have to know it to read the article! You just have to know what a cosine is! I learned what a cosine was in eighth grade because I wanted to program a game where objects would fly across the screen at a constant velocity but a varying angle. You can learn it too!

He's not, like, invoking the convolution theorem or anything in those quotes. Although he does get into it a bit.

I think that, if you know the convolution theorem and Euler's formula, things like the production of sum and difference frequencies from the multiplication of sinusoids start to seem obvious rather than sort of random. When I was in high school they seemed sort of random. My uncle had tried to explain Euler's formula to me, along with the Taylor expansions for sine, cosine, and the exponential, but I hadn't really understood, because I didn't have the background knowledge to appreciate them then.

Re: Radios, how do they work? (2024)

#43

Post by zppln »

lormayna wrote: post #40
mholt wrote: post #27

Earlier quoted context omitted.

I 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…

Antennas are really black magic: optimizing an antenna requires stocastich method like genetic algorithms, simulated annealing, etc. Moreover if you want to model the radiation patterns and the electrical characteristics you need to use finite element calculation methods. So, you need a lot of computation power as antenna are not a problem that can be solved in a closed form. Source: I almost burnt my PC on simulatin…

Related: https://en.wikipedia.org/wiki/Evolved_antenna

Re: Radios, how do they work? (2024)

#44

Post by akerl_ »

DrAwdeOccarim wrote: post #16
tiniuclx wrote: post #7

I'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.

Do 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.

A random plug for https://hamstudy.org/

The US ham test question pools are fully public. Your test will be a mixture of questions from the pool. HamStudy basically lets you churn the question pool, and then will offer explainer text / references to back up each question and correct answer.

I went on a vacation and used their phone app any time I was standing in a line. You can set it to just keep spinning through the questions, with a bias towards ones you're getting wrong.

Re: Radios, how do they work? (2024)

#45

Post by cfraenkel »

mkipper wrote: post #37
mholt wrote: post #27

Earlier quoted context omitted.

I 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…

I work in software now, but I have an electrical engineering degree and started my career on a project developing a radio. Our project probably had ten or more electrical engineers on it, and only one or two of them really understood the RF side of it. It's a very specialized skill -- even EEs with >20 years of experience would describe things as black magic. So I don't think you're alone feeling this way. Even with…

A long time ago, worked on a comm satellite program. It used a whack of tuned cans to combine high powered transmit signals with harmonics in each others' frequency bands to feed into the antenna. I once asked how they worked. The answer was 'magic'. I mean, they were physical RF filters, but no one could explain or reproduce how they worked. There was this one guy who could tighten the screws that adjusted the inside baffles so they 'worked'. No one else could.

Re: Radios, how do they work? (2024)

#46

Post by pengaru »

tigereyeTO wrote: post #24

> 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 sinus…

What do you consider advanced math? This isn't solving differential equations...

Re: Radios, how do they work? (2024)

#47

Post by kragen »

dd_xplore wrote: post #9

To 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.

Crystal radios don't normally contain crystal oscillators, which do require a battery source. Perhaps you mean a crystal rectifier.

Re: Radios, how do they work? (2024)

#48

Post by kragen »

gtsnexp wrote: post #13
immibis wrote: post #10

Earlier quoted context omitted.

The crystal radios I know don't have crystal oscillators - the word "crystal" refers to the diode.

https://www.youtube.com/watch?v=-GxL13rid1w

This 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.

Re: Radios, how do they work? (2024)

#49

Post by richiebful1 »

mholt wrote: post #27
tigereyeTO wrote: post #24

> 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 sinus…

I 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…

I've had my ham license for ten years, but I've only ever used a basic car-based mobile setup and my handhelds. My morse code speed is abysmal. QRP and all that are really cool, but I just use ham radio to supplement my fire/ems handheld in a natural disaster.

Re: Radios, how do they work? (2024)

#50

Post by Aloha »

pkolaczk wrote: post #14
dd_xplore wrote: post #9

To 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.

You 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 ca…

I have used a synchronous AM detector once in a radio, its a game changer for listening to shortwave.
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