91–100 of 114 posts
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.
This is an excellent article, thank you for submitting it! I love how effortlessly this article delivered an intuition for why an ideal antenna length would be half of the wavelength of the signal you want to receive. I was also delighted by the point about how all methods of modulating a wave can be recontextualized as frequency modulation!
> 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…
There's old modulation techniques that are crazy efficient too - the most obvious one being GPS. A small antenna, just 2cm short [1], is all you need to pick up and distinguish from each other the signal of up to a dozen different GPS and dozens of other (GLONASS, Galileo, BeiDou) navigation satellites. This is mind-blowingly nuts.
For modern high-bandwidth communication, microwave point-to-point links can achieve 65km range with barely 4 watts of RF energy - e.g. German Telekom's Skylink system connecting an aviation radio transmitter on the island of Helgoland with the continental backbone at Cuxhaven [2]. And actually that is way more power than required, half a watt is enough but they chose to go for higher power to achieve perfect reliability even in worst-case conditions [3] (does make sense, given how safety-critical flight radio communication is).
If all you need is satellite communication for a few bytes of information, a cellphone can send an emergency message to satellites anywhere on this planet (at least, where regulatory clearances allow for that) [4].
[1] https://electronics.stackexchange.com/questions/586900/how-c...
[2] https://www.youtube.com/watch?v=q_Ja6QtWwpQ
[3] https://www.telekom.com/de/blog/netz/artikel/skylink-richtfu...
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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!
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"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…
Re cell phones, I'll just say this. RF engineering went through a revolution about 10 to 15 years before cell phones became commonplace. The electronics shrunk in size by an order of magnitude, the RF front ends including its transistors increased their FT (transition/cutoff frequency) by over an order of magnitude, and the noise figure of RF front ends was reduced to well below 1dB.
The net/combined result of these three improvements in RF engineering was a truly remarkable achievement. Fact is, there'd be no smartphones or integrated GPS without these developments all having happened. I'd also add that by and large programmers simply haven't a clue about this very special aspect of RF engineering. They just take for granted that the hardware does what it says, to them it's just a black box.
Programming, which cannot be really called engineering because many decades on, it's still an undisciplined way of working that's more akin to an art form than true professional engineering, can however provide the glitz factor that sells phones, but it's completely lost without the state-of-art RF hardware substrate upon which it sits. Moreover, the next revolution in phone technology such as direct satellite services, will only be practical after a further revolution in RF hardware (what passes for some showy demos today is nowhere near the mark if the tech is to be widely adopted).
If you think I've been too hard on programming then I'd suggest you read this near 30-year-old SciAm article as starting point: https://www.researchgate.net/publication/247573088_Software'....
Thirty years on essentially programming has adopted some new techniques for developing software but the fundamental underlying problem of the lack of rigorous standards together with proven methods to solve problems by computer remains unresolved, and in some instances the software industry has gotten demonstrably worse.
I've not the time to put current references that support my claim but a search will soon find them—ones written by both authoritative people within the programming industry and elsewhere such as in computer science research.
Would it be possible to construct a rudimentary FM radio receiver with only the most basic parts ala Masters of the Air?
A classic passive RC or LC or RL filter, will cause a phase shift. Take the difference between two phases effectively decodes FM. No active elements required. With only RL filters it would be very inefficient. So you may need to be standing next to the transmitter if you don't have at least one transistor or tube. But one such tube or transistor would be plenty for a strong local broadcast.
If you have some capacitors, it gets easier. Maybe paper and tinfoil rolled tightly, or flakes of glass or mica between thin slices of wood. Check out the slope detector circuits here [1] (fig 3, 4); the article is a good introduction to FM detection in general.
[1] https://wiki.analog.com/university/courses/electronics/elect...
Their primer article [1] is also really nice. > Today, I’d like to close this gap with a couple of crisp definitions that stay clear of flawed hydraulic analogies, but also don’t get bogged down by differential equations or complex number algebra. Related: many, many years ago, when Facebook didn't exist yet, Google still passed as a "good" company, and hobbyist electronic geeks had almost only PICs to choose from, I…
>flawed hydraulic analogies I want to say that’s cool, avoid common pitfalls in explanations, but I want to to point out that all analogies fall short, otherwise they would be the same thing, and not an analogy. That is, if the hydraulic analogy were perfect, then that would mean that electronics would just behave as a fluid and we could teach it an a part of fluid dynamics. But instead it is an analogy, electronics…
We can use water to explain why capacitors in series have less capacitance!
I'm now thinking whether we could build a water pressure multiplier using the cascade voltage multiplier topology.
https://en.wikipedia.org/wiki/Voltage_multiplier
Use some rubber dams or flexible pipes for the capacitors, one-way backstop valves for the diodes, and then some back-and-forth pumping mechanism to generate water AC. It should work.
Their primer article [1] is also really nice. > Today, I’d like to close this gap with a couple of crisp definitions that stay clear of flawed hydraulic analogies, but also don’t get bogged down by differential equations or complex number algebra. Related: many, many years ago, when Facebook didn't exist yet, Google still passed as a "good" company, and hobbyist electronic geeks had almost only PICs to choose from, I…
I guess the original "NEETS" content is this: http://compatt.com/Tutorials/NEETS/NEETS.html Content updated in 2011.
Earlier quoted context omitted.
I guess the original "NEETS" content is this: http://compatt.com/Tutorials/NEETS/NEETS.html Content updated in 2011.
Hmm... Unfortunately the site is infested with spam links - visible with ad blockers turned on.
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It's because energy created by the transmitter must degrade as one over R squared in the far field. The frequency (or wavelength, have your pick) has nothing to do with the energy transmitted because energy must be conserved. Putting in the frequency term then violates conservation of energy between the antennas. Then, at the receiving antenna the error of conservation of energy is then patched up by assigning a bogu…
The formula on wiki has a distance squared term in the denominator tho?
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I guess the original "NEETS" content is this: http://compatt.com/Tutorials/NEETS/NEETS.html Content updated in 2011.
Hmm... Unfortunately the site is infested with spam links - visible with ad blockers turned on.