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.
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.
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.
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.
As someone who's always dabbled in electronics, skimmed and read some books, my primary complaint abot most electronics texts is that they just talk about individual topics: oscillators, amplifiers, etc.
What they never talk about, is putting them all together.
But as witnessed by this list, that's what a radio is. A collection of these "meta" components into a whole to get a better radio experience.
A radio built like this, with individual subsystems connected together, is much more understandable. Many (not all) radio schematics are presented as a whole, rather than the parts, or why you might (or might not) want to change one part or another (not components, but one, say, filter circuit to a different one).
It just seems to me that once you get past some basic theory, starting with a radio, and then systematically taking it apart is a better way of approaching electronics education.
Haha I know! When I was even younger, we had a radio that could recieve SW,AM,MW,FM(in TV range as well).
I used to hook up the antenna to various things like wire mesh or tv antennas etc and used to listen to short wave and AM for hours. I even got signals from far away countries, it was really fascinating!
Also I had seen some recon antennas in a certain campus (can't say much about that) when I was a kid. Those were like long wires hanging from towers. I believe they used to receive/decode SW/AM signals from far away. I realised this much much later in my life. But fascinating nonetheless.
And adding to all these is SDR! That's a whole different thing.
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.
My 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.
If 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.
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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.
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.
The Extra exam is 50 multiple choice questions broken down by category as follows:
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.
Dead Comment
It was mind blowing when I first heard the audio through IEMs ! It felt magical that this contraption was working without any battery source.
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!
As someone who's always dabbled in electronics, skimmed and read some books, my primary complaint abot most electronics texts is that they just talk about individual topics: oscillators, amplifiers, etc.
What they never talk about, is putting them all together.
But as witnessed by this list, that's what a radio is. A collection of these "meta" components into a whole to get a better radio experience.
A radio built like this, with individual subsystems connected together, is much more understandable. Many (not all) radio schematics are presented as a whole, rather than the parts, or why you might (or might not) want to change one part or another (not components, but one, say, filter circuit to a different one).
It just seems to me that once you get past some basic theory, starting with a radio, and then systematically taking it apart is a better way of approaching electronics education.
Also I had seen some recon antennas in a certain campus (can't say much about that) when I was a kid. Those were like long wires hanging from towers. I believe they used to receive/decode SW/AM signals from far away. I realised this much much later in my life. But fascinating nonetheless. And adding to all these is SDR! That's a whole different thing.
Or a razor blade or a piece of roofing lead and a needle.
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.
Radios, how do they work? - https://news.ycombinator.com/item?id=39813679 - March 2024 (109 comments)
https://sg30p0.familysearch.org/service/records/storage/dasc...
https://www.youtube.com/watch?v=9LsJn0CyyZI
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.