> 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.
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 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.
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.
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.
I'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.
EDIT: 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.
> 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.
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 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.
It 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!
To be fair, they did qualify it as "advanced" math :-)
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.
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
You 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
You have to memorize a long questionnaire in the US (though in English) to get it there, too.
Great advice!
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 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!
The crystal radios I know don't have crystal oscillators - the word "crystal" refers to the diode.
https://www.youtube.com/watch?v=-GxL13rid1w
I'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.
Previously:
Radios, how do they work? - https://news.ycombinator.com/item?id=39813679 - March 2024 (109 comments)
Never thought about the AM bandwidth thing before that is interesting and seems obvious now (from Fourier Transform point of view)
Here's a video of AM modulation. SDR transmitter (running GNU Radio) connected to an SDR receiver.
https://www.youtube.com/watch?v=9LsJn0CyyZI
This reminds me of a beautiful book written by Paul Nahin, 'The Science of Radio'.
Bought it but never read it - is it worth pushing through?
Cool article; I’m still baffled though.
The article is interesting but some images have Error 400 so I can’t see them.
Probably just a network hiccup.
I ran into the same thing earlier, but it worked fine after a couple refreshes.
needs more pictures!
EDIT: 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.