Radios, how do they work? (2024) • Hacker News Board

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

#31

Post by hedgehog » Thu, Oct 23, 2025, 4:08 PM UTC

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…

Even 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.

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

#32

Post by tzs » Thu, Oct 23, 2025, 4:09 PM UTC

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.

Take 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.

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

#33

Post by _whiteCaps_ » Thu, Oct 23, 2025, 4:18 PM UTC

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'd love to see more people on the air. My advice is to get a radio with a good tuner, build a simple dipole with the online calculators, and try to make contacts that way.

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

#34

Post by ux266478 » Thu, Oct 23, 2025, 4:21 PM UTC

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 assure you, that doesn't go away in electrical engineering or even theoretical physics. Electromagnetism exhibits a large degree of behavioral emergence. It's one of the most well studied aspects of physics, but remains a rather convoluted and seemingly arbitrary puzzle box of nonsense especially at a macroscopic level.

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

#35

Post by jandrese » Thu, Oct 23, 2025, 4:25 PM UTC

tzs wrote: post #32

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.

Take 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 t…

As I understand it General gets you most everything and Extra is mostly useful for people who want to teach amateur radio classes.

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

#36

Post by peterfirefly » Thu, Oct 23, 2025, 4:25 PM UTC

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…

Are you objecting to the trivial extension to cos(α - β)? The cos(α + β) identity itself is nicely explained in the text.

The third thing you quote is the result of fairly simply symbol manipulation that requires no new knowledge apart from the original cosine identity and the obvious corollary about subtracting an angle being the same as adding a negated one.

There is zero advanced math there. No complex numbers, no calculus, no limits, no Fourier, no "functions are vectors, too".

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

#37

Post by mkipper » Thu, Oct 23, 2025, 4:26 PM UTC

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 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 good foundation in the theory and math, I think most people hit a wall with radios at some point. All the people I worked with who intuitively "got" RF stuff had been doing nothing else professionally for over a decade.

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

#38

Post by andoando » Thu, Oct 23, 2025, 4:34 PM UTC

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…

How I wish I could quit my job and go back to school.

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

#39

Post by Isamu » Thu, Oct 23, 2025, 4:43 PM UTC

peterfirefly wrote: post #36

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…

Are you objecting to the trivial extension to cos(α - β)? The cos(α + β) identity itself is nicely explained in the text. The third thing you quote is the result of fairly simply symbol manipulation that requires no new knowledge apart from the original cosine identity and the obvious corollary about subtracting an angle being the same as adding a negated one. There is zero advanced math there. No complex numbers, no…

To be fair, I think most people regard “not advanced math” to exclude trig, and maybe algebra too. Fear and loathing of math is a thing.

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

#40

Post by lormayna » Thu, Oct 23, 2025, 4:44 PM UTC

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…

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 simulating a dipole array while studying for the antennas course at the university