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Radios, how do they work?

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Re: Radios, how do they work?

#81

Post by pfdietz »

hilbert42 wrote: post #67
pfdietz wrote: post #59

I'm intrigued by things like this that used to be high technology but now are mature and pushed way down into the infrastructure. No one is going to make much money being really good at radio, any more than they will be really good at machining steel, but it's still necessary for higher levels of the tech stack to function.

"No one is going to make much money being really good at radio, any more than they will be really good at machining steel," How do you know? For instance, I'd suggest that not every method of modulation has been invented or even yet implemented. Also, we've hardly begun to design and implement meta materials into antennae and RF filters—the field's still wide open for innovation and invention. And new methods of 'mac…

The point I was trying to make was that these things are no longer what determines success or failure. Incremental improvements are possible, but do not dominate.

Consider the fight between a company that's great at RF design, and a company that's on top on software. Which do you think will win in the market for cell phones? (This is a trick question.)

Mature technologies tend to be things that can be outsourced. So one can make some money (if not a lot) as a supplier of these things in a horizontally integrated industry.

Re: Radios, how do they work?

#82

Post by Isamu »

IndrekR wrote: post #74
Isamu wrote: post #68

Also, I’m not sure if people are aware of the number of radio systems that enable their smartphones. NFC (eg. Apple Pay) is a radio, range a few cm. Bluetooth is a radio, a few meters. WiFi is several radio systems, range tens of meters. Cell phone is several radio systems, range up to kilometers. GPS (and rival systems) range up to thousands of kilometers.

NFC is not really a radio. Basically it uses a loosely copled transformer. Works much closer than 1 wavelength and only magnetic field matters.

Good point, NFC is described as operating in a particular RF band but not through radio waves:

> As with proximity card technology, NFC uses inductive coupling between two nearby loop antennas effectively forming an air-core transformer. Because the distances involved are tiny compared to the wavelength of electromagnetic radiation (radio waves) of that frequency (about 22 metres), the interaction is described as near field. An alternating magnetic field is the main coupling factor and almost no power is radiated in the form of radio waves (which are electromagnetic waves, also involving an oscillating electric field); that minimises interference between such devices and any radio communications at the same frequency or with other NFC devices much beyond its intended range. NFC operates within the globally available and unlicensed radio frequency ISM band of 13.56 MHz. Most of the RF energy is concentrated in the ±7 kHz bandwidth allocated for that band, but the emission's spectral width can be as wide as 1.8 MHz[57] in order to support high data rates.

https://en.m.wikipedia.org/wiki/Near-field_communication

Re: Radios, how do they work?

#83

Post by jacobolus »

hagbard_c wrote: post #79
jameshart wrote: post #72

> In today’s article, I’m hoping to provide an introduction to radio that’s free of ham jargon and advanced math. Sounds great! Let’s dig in. > … the fundamental mirroring behavior is still present, but it’s usually managed pretty well. Accidental mirror images of unrelated transmissions can be mitigated choosing the IF wisely, by designing the antenna to have a narrow frequency response, or by putting an RF lowpass…

Not really unless you refer to the use of 'IF' and 'RF'. Maybe it would have been better if they wrote these out as 'IF (intermediate frequency)' and 'RF (radio frequency)' with a link to explain in which context IF is used but for the rest that sentence looks OK to me.

The meaning of "mirroring behavior", "narrow frequency response", "lowpass filter", "mixer", "IF", "RF" are all unexplained both in this article and the listed prerequisite articles.

The meaning of "mixer" might be inferred from the earlier "the basic operation of almost every radio receiver boils down to mixing (multiplying) the amplified antenna signal with a sine wave of a chosen frequency." And the meaning of "mirroring behavior" might be inferred from the earlier "we can see that every peak of the driving signal reaches the ends of the antenna perfectly in-phase with the bounce-back from the previous oscillation". But these are still explanations that rely on a good amount of past expertise and other jargon not covered in this or the author's other pages, which probably has to involve quite a lot of what most people would consider "advanced math", though as always "advanced" is relative, or alternately a lot of direct experience playing with analog signals.

Re: Radios, how do they work?

#84

Post by Animats »

somat wrote: post #24
Animats wrote: post #5

Earlier quoted context omitted.

> I was also delighted by the point about how all methods of modulating a wave can be recontextualized as frequency modulation! That's the classic way to think about it. Another way is to view the input as simply a sequence of voltage readings. Extracting a useful signal from that is an exercise in exploiting redundancy in noisy data. [1] Software defined receivers work that way. Analog radio (AM, FM, etc.) is a hulk…

I may not be understanding what part of the operation you are talking about. but radiated power? no transmitter had megawatts of radiated power. 50Kw for a fm broadcast antenna is a common number passed around. The huge "voice of america" shortwave station was 300Kw. I have heard of military radars having megawatts of radiated power. but even then it was in the low megawatts.

Up in the UHF TV bands, huge transmitter power was required. The FCC allowed 5 megawatts.[1] Few stations actually used that much power, but 1 MW was not uncommon.

Amusingly, over-the-air digital TV is making a comeback. The cable industry pushed prices up too high. But the "comeback" is to only 14% of the viewer base.

[1] https://en.wikipedia.org/wiki/UHF_television_broadcasting

Re: Radios, how do they work?

#85

Post by tonymet »

Learning radio can help improve your skills in understanding the analog underpinnings of networking, CPUs , electronics & circuits .

So many issues come about by taking these for granted. EMF interference , a short circuit or a noisy power supply can cause non-deterministic issues that will drive you mad unless you are aware of the root cause.

Re: Radios, how do they work?

#86

Post by [deleted] »

martinky24 wrote: post #64
pfdietz wrote: post #59

I'm intrigued by things like this that used to be high technology but now are mature and pushed way down into the infrastructure. No one is going to make much money being really good at radio, any more than they will be really good at machining steel, but it's still necessary for higher levels of the tech stack to function.

The US (and Chinese, and Russian, and European...) government spends billions a year on companies that are good at radio. Radar, satellite communications, 5G, etc, etc. are all critical parts of modern technology stacks, that are "high technology", and key for forward innovation. If you think it's a solved problem, why doesn't every telecom company have nationwide 5G deployed yet? There is A LOT of money to be made i…

[deleted]

Re: Radios, how do they work?

#87

Post by albert_e »

nonninz wrote: post #47
helsinkiandrew wrote: post #28

Earlier quoted context omitted.

I guess the original "NEETS" content is this: http://compatt.com/Tutorials/NEETS/NEETS.html Content updated in 2011.

THAT'S IT!!! Thank you so much! I've been looking for this for at least fifteen years! And there are even links to previous HTML versions (this one is PDF)... amazing!

Amazing thanks for remembering a great resource that you saw years ago. Seems very comprehensive. Bookmarking this.

Re: Radios, how do they work?

#88

Post by [deleted] »

pfdietz wrote: post #81
hilbert42 wrote: post #67

Earlier quoted context omitted.

"No one is going to make much money being really good at radio, any more than they will be really good at machining steel," How do you know? For instance, I'd suggest that not every method of modulation has been invented or even yet implemented. Also, we've hardly begun to design and implement meta materials into antennae and RF filters—the field's still wide open for innovation and invention. And new methods of 'mac…

The point I was trying to make was that these things are no longer what determines success or failure. Incremental improvements are possible, but do not dominate. Consider the fight between a company that's great at RF design, and a company that's on top on software. Which do you think will win in the market for cell phones? (This is a trick question.) Mature technologies tend to be things that can be outsourced. So…

[deleted]

Re: Radios, how do they work?

#89

Post by pests »

dTal wrote: post #76
Isamu wrote: post #68

Also, I’m not sure if people are aware of the number of radio systems that enable their smartphones. NFC (eg. Apple Pay) is a radio, range a few cm. Bluetooth is a radio, a few meters. WiFi is several radio systems, range tens of meters. Cell phone is several radio systems, range up to kilometers. GPS (and rival systems) range up to thousands of kilometers.

...and yet, efficiently transferring a 1kb file between two physically adjacent smartphones remains an apparently unsolved problem.

AirDrop it?

Re: Radios, how do they work?

#90

Post by cbfrench »

TrackerFF wrote: post #33

I think it is also worth mentioning the role of the ionosphere - which is the (charged) part of the atmosphere that will reflect radio/EM waves, and make it possible to communicate with someone on the other side of the globe. The ionosphere has different layers, and is quite dynamic - depending on the sun and its activity. Basically, imagine a charged shell around the earth that reflects electromagnetic waves back, a…

> Solar storms (and following northern lights) are bad news for radio communication.

Although it can allow for auroral backscatter propagation on VHF, which is fascinating. https://www.electronics-notes.com/articles/ham_radio/amateur...

Definitely not good for HF though. The Sun wilding out the past few days has at least given me the opportunity to work on some stuff in the evenings that isn’t screwing around on FT8, lol.

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