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Radios, how do they work?

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Re: Radios, how do they work?

#101

Post by Robin_Message »

mschuster91 wrote: post #92
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…

> Modern modulation techniques are insanely efficient. It's amazing that mobile phones work. 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…

I love the fact that GPS signals are below the noise floor; its only through correlating the complex modulation that you can find the signal. At least, that's how I understood it when I did my degree!

Re: Radios, how do they work?

#102

Post by dTal »

pests wrote: post #89
dTal wrote: post #76

Earlier quoted context omitted.

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

AirDrop it?

I'm sure that works beautifully, unless one or both parties happen to be running the most popular mobile OS in the world, Android. That 'AirDrop' even exists as a proprietary technology really proves the point.

Re: Radios, how do they work?

#103

Post by AtomicOrbital »

Essence of radio is very simple ... radio station broadcasts a high power RF signal into which some human listenable audio (your favorite singer's song) is mixed ... so the radio station propagates this RF signal modulated by the song being played ... across town at your house your radio synthesizes an RF signal identical to that broadcast from the radio station ... your radio amplifies the result of combining its local RF signal together with the received RF signal from the radio station ... this combining will add together both RF signals it will also subtract both ... when it subtracts ( wave interference ) the result is the difference between the radio station modulated RF signal and your radio RF signal (both at identical frequencies) which leaves you with just the song

Re: Radios, how do they work?

#105

Post by pbnjeh »

a_w wrote: post #97
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.

Hmm... Unfortunately the site is infested with spam links - visible with ad blockers turned on.

Replying to sibling comments: The links are there, but are hidden by Javascript. Since I'm on my phone, I didn't look into how.

Re: Radios, how do they work?

#106

Post by drivers99 »

pbnjeh wrote: post #105
a_w wrote: post #97

Earlier quoted context omitted.

Hmm... Unfortunately the site is infested with spam links - visible with ad blockers turned on.

Replying to sibling comments: The links are there, but are hidden by Javascript. Since I'm on my phone, I didn't look into how.

What's a spam link? I don't see anything unusual. Can you post a screenshot (using imgur or something)?

Re: Radios, how do they work?

#107

Post by ianburrell »

dTal wrote: post #102
pests wrote: post #89

Earlier quoted context omitted.

AirDrop it?

I'm sure that works beautifully, unless one or both parties happen to be running the most popular mobile OS in the world, Android. That 'AirDrop' even exists as a proprietary technology really proves the point.

On Android, use Android Quick Share which uses Google Nearby. It works very similarly to Air Drop including support for UWB.

There are lots of things where Apple and Google have solutions that don't work together.

Re: Radios, how do they work?

#108

Post by hilbert42 »

Aloha wrote: post #80
hilbert42 wrote: post #63

Earlier quoted context omitted.

Ha, not magic but conceptually the superhetrodyne is an absolutely brilliant design and it's still not lost is 'magic' even after a hundred years, and likely never will despite newer digital concepts (they being more complex to implement). "Edwin Armstrong was a brilliant brilliant man." Right! ...And as you'd likely know, Armstrong's tormentor and nemesis was an arrogant, despicable bastard of the first order! (Beli…

It was in part reference to "Any sufficiently advanced technology..." So, you worked for RCA.. here is a question that there is no good book on, but what killed RCA, and what was it like working there? I dont know what I think of Sarnoff - not sure I'd use evil - he was a "no niceties" fiercely competitive capitalist for sure - and how you feel about that may vary, Armstrong was also an extremely hard headed man, and…

"...what killed RCA, and what was it like working there?"

Two good questions. Haven't time to reply in detail now but I'll do so shortly with what I know, and how I met Sarnoff, and about working there (in short, it was an excellent job).

Re: Radios, how do they work?

#109

Post by luyu_wu »

AtomicOrbital wrote: post #103

Essence of radio is very simple ... radio station broadcasts a high power RF signal into which some human listenable audio (your favorite singer's song) is mixed ... so the radio station propagates this RF signal modulated by the song being played ... across town at your house your radio synthesizes an RF signal identical to that broadcast from the radio station ... your radio amplifies the result of combining its lo…

That's not what the article is about... Many people lack details on how antenna designs are optomized and the application of Faraday and Lenz's law in signal propogation. This is what the article addresses.

Re: Radios, how do they work?

#110

Post by drivers99 »

drivers99 wrote: post #106
pbnjeh wrote: post #105

Earlier quoted context omitted.

Replying to sibling comments: The links are there, but are hidden by Javascript. Since I'm on my phone, I didn't look into how.

What's a spam link? I don't see anything unusual. Can you post a screenshot (using imgur or something)?

(replying to myself since I can't edit) In retrospect, I wonder if [the person I'm replying to] was referring to a different link in this thread, such as the rimstar one, which is pretty bad.
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