Craig's Science topics #5: radio waves are amazing

[Craig234]

When you think about it, where you are sitting right now, all around you there are all kinds of conversation, music, and other data being sent. In the air, invisible, around you.

What's amazing especially is how these things don't conflict.

Think about listening to sound - if you hear all the radio stations played at once, it's just a big noise.

It's a big deal for one station to be able to be transmitted - but to have more than one and even many, all transmitted in the same location, without interfering with each other - amazing.

 

[IronWing]

Hearing uses spread frequency signals so we have to listen to more than one freq at a time to make sense of the signal. This also brings in all the noise so we have to determine which sounds to ignore in post processing. In radio, we intentionally monitor only one freq at a time, filtering out all the others up front.

 

[herm0016]

When you think about it, where you are sitting right now, all around you there are all kinds of conversation, music, and other data being sent. In the air, invisible, around you.

What's amazing especially is how these things don't conflict.

Think about listening to sound - if you hear all the radio stations played at once, it's just a big noise.

It's a big deal for one station to be able to be transmitted - but to have more than one and even many, all transmitted in the same location, without interfering with each other - amazing.

they do interfere, we just have built receivers well enough to figure out what they are listening for.

ex: a cheap led light bulb in my garage causes the wireless openers not to work because of interference.

 

[agent00f]

When you think about it, where you are sitting right now, all around you there are all kinds of conversation, music, and other data being sent. In the air, invisible, around you.

What's amazing especially is how these things don't conflict.

Think about listening to sound - if you hear all the radio stations played at once, it's just a big noise.

It's a big deal for one station to be able to be transmitted - but to have more than one and even many, all transmitted in the same location, without interfering with each other - amazing.

The amazement is predicted on the fact that various objects in nature reliably move near certain frequencies, which is a result of how basic physical forces work, and the mathematical reality that various frequencies of vibration can be isolated from any such movement.

It took some time for people to figure out how to harness all this for artificial pursuits.

 

[Craig234]

they do interfere, we just have built receivers well enough to figure out what they are listening for.

ex: a cheap led light bulb in my garage causes the wireless openers not to work because of interference.

When I say interfere, what I mean is, unlike playing 100 radio stations at the same time so it's just a noise, all 100 are in the same space and you can listen to any one without the others destroying it.

 

[agent00f]

When I say interfere, what I mean is, unlike playing 100 radio stations at the same time so it's just a noise, all 100 are in the same space and you can listen to any one without the others destroying it.

As noted, frequency transforms are literally math. If anyone's curious "why" that is: https://www.dartmouth.edu/~matc/MathDrama/reading/Wigner.html

 

[SMOGZINN]

When I say interfere, what I mean is, unlike playing 100 radio stations at the same time so it's just a noise, all 100 are in the same space and you can listen to any one without the others destroying it.

I'm assuming you are meaning that if you had 100 radios each playing a different song it would all just sound like noise to you. But that is because your mind is not filtering it properly. You are capable of filtering it if you try hard enough. An example of this is if one of those 100 radios started to play a repeating track of someone saying your name you would be able to pick it out right away, and even with just a little work point to the specific speaker that your name is coming from.

 

[agent00f]

I'm assuming you are meaning that if you had 100 radios each playing a different song it would all just sound like noise to you. But that is because your mind is not filtering it properly. You are capable of filtering it if you try hard enough. An example of this is if one of those 100 radios started to play a repeating track of someone saying your name you would be able to pick it out right away, and even with just a little work point to the specific speaker that your name is coming from.

I'm pretty sure he means tuning, though in fairness the nuance is lost here.

 

[Craig234]

I'm assuming you are meaning that if you had 100 radios each playing a different song it would all just sound like noise to you. But that is because your mind is not filtering it properly. You are capable of filtering it if you try hard enough. An example of this is if one of those 100 radios started to play a repeating track of someone saying your name you would be able to pick it out right away, and even with just a little work point to the specific speaker that your name is coming from.

Another example is the 'buzz' of conversation in a crowd like a restaurant. You have a very small option to try to single out a conversation.

But think of my point also like throwing several rocks in a pond, how the waves from each change the others.

 

[MongGrel]

Its pretty amazing the Intertoobs don't get clogged up a lot either.

I'm just saying.

 

[agent00f]

Its pretty amazing the Intertoobs don't get clogged up a lot either.

I'm just saying.

Not just saying but a relevant point. Electronic communication over a wire uses the same tech/math as radio in the same layer, just a different physical medium. Somewhat differing but conceptually akin math/"logic" is used to distinguish messages at higher levels.

 

[Craig234]

Its pretty amazing the Intertoobs don't get clogged up a lot either.

I'm just saying.

I'm not that familiar with the similarity to the physical connections. As far as wireless - it can be similar but since so much uses the same frequencies they can conflict.

 

[agent00f]

I'm not that familiar with the similarity to the physical connections. As far as wireless - it can be similar but since so much uses the same frequencies they can conflict.

The whole point of FCC oversight (ie freq auctions) is that they don't.

 

[Dr. Zaus]

We have a built in frequency band - we don't hear sounds outside of about 20 Hz to 20 kHz.

 

[Mike64]

We have a built in frequency band - we don't hear sounds outside of about 20 Hz to 20 kHz.

And most of us can't hear that. Especially at the upper end of the range. The upper limit pretty much plummets between the ages of about 8 and 20, and then continues a more gradual, but basically lifelong, decline to an extent that many people simply refuse to believe. (I'm thinking "audiophile" type people here, many of whom are quick to insist, without blind testing, that they personally have outlying "exceptional" hearing...)

ETA:

without interfering with each other - amazing.

They very definitely interfere on a wavelength/frequency basis, there's simply no way around the interaction between those moving airwaves. As others have mentioned, that's just basic physics.

An easy example of this is that it's (literally) physically impossible to "hear" an individual instrument's "unique" sound when played in an orchestra. If you're familiar with their individual sounds, you can pick out which instruments are playing what, when (even to the extent of first/second/third instruments/groups of instruments playing different parts of the score), but the canceling out and reinforcement of the many primary frequencies (never mind the harmonics) being produced at the same time, especially in close proximity to each other, means that what you "hear" is the sum total of the "orchestra", not simply a "group of instruments playing at the same time"... That's why, among other things, it's pretty easy for a familiar ear (let alone a trained one) to distinguish between even trios, quartets, chamber groups, etc. without listening very long or carefully - they each have a pretty distinctive "overall sound".

Distinguishing among various sound sources in the environment is far more about neurological processing than "sound detection". Which is also why people typically learn to speak a new language themselves more easily/better than they understand others speaking it. I forget the numbers, but we actually "hear" a surprisingly low percentage of what other people say - our brains "fill in" the rest based largely on context, and until you know a language pretty well, that just can't be done with any reliability. It's also a big part of the reason we so often mishear what we only casually overhear, and why so many of us basically make up out of whole cloth most of the lyrics to pop music we hear on the radio or other low fidelity sources... (That last case is so particularly egregious because in most cases, songs don't tell a coherent enough "story" to make much sense of many of the individual words and phrases.)

 

[agent00f]

They very definitely interfere on a wavelength/frequency basis, there's simply no way around the interaction between those moving airwaves. As others have mentioned, that's just basic physics.

He was talking about sound sent over radio waves, not sound in air per se. There's some nuance in that case where the sound is encoded, even if crudely, onto a very specific carrier frequency which can be more easily tuned/filtered by electronic equipment. Easier compared to picking out natural sounds in air.

 

[Mike64]

He was talking about sound sent over radio waves, not sound in air per se. There's some nuance in that case where the sound is encoded, even if crudely, onto a very specific carrier frequency which can be more easily tuned/filtered by electronic equipment. Easier compared to picking out natural sounds in air.

Ah, OK. I guess the statement

Think about listening to sound - if you hear all the radio stations played at once, it's just a big noise.

and others' comments about sound in general threw me.

But RF/EMF frequencies also do in fact interact in the same basic ways - hence the ability to "jam" transmissions with other, appropriately tuned, ones and/or just by overpowering them. The fact that they don't generally interfere with each enough to prevent acceptable reception isn't a random or "natural" phenomenon, but is due to the overall system of EMF frequency usage (adequate frequency separation, geographic separation of transmitters, and the legal ban on unlicensed transmissions, or at least those above very low power limits) established by a combination of governmental regulations, and to a lesser extent, industry standards and conventions based on "enlightened self-interest" ("I won't mess with your transmissions so you won't/if you don't mess with mine …")

 

[Craig234]

Ah, OK. I guess the statement and others' comments about sound in general threw me.

Right that was an analogy, not the topic, as sound doesn't have the same amazing quality.

But RF/EMF frequencies also do in fact interact in the same basic ways - hence the ability to "jam" transmissions with other, appropriately tuned, ones

Yes, transmitting on the same frequency causes that conflict - but it's the co-existence of many 'frequencies' in the same physical space that's amazing.

 

[Mike64]

Right that was an analogy, not the topic, as sound doesn't have the same amazing quality.

Yes, transmitting on the same frequency causes that conflict - but it's the co-existence of many 'frequencies' in the same physical space that's amazing.

But that's really not the case. Broadly and conceptually speaking, the interaction of radio waves isn't vastly different from the interaction of sound waves (or waves in fluids). But radio receivers are much more specialized than human ears and nervous systems. If could build a radio that could "hear" everything over a wide range of frequencies at the same time, radio reception would be just as chaotic as human hearing can be. It's mostly the fact the fact that "radios" are tuned to specific, isolated frequencies at any given time that makes it seem like the transmissions they're picking up are co-existing more "cooperatively" than they in fact are.

 

[agent00f]

But that's really not the case. Broadly and conceptually speaking, the interaction of radio waves isn't vastly different from the interaction of sound waves (or waves in fluids). But radio receivers are much more specialized than human ears and nervous systems. If could build a radio that could "hear" everything over a wide range of frequencies at the same time, radio reception would be just as chaotic as human hearing can be. It's mostly the fact the fact that "radios" are tuned to specific, isolated frequencies at any given time that makes it seem like the transmissions they're picking up are co-existing more "cooperatively" than they in fact are.

The second part of his post that math works so well on waveforms is actually pretty amazing, per my link in #6 above. There really isn't any satisfying explanation for this that I've been able to find, in the realm of technical reasons at least.

 

[Craig234]

But that's really not the case. Broadly and conceptually speaking, the interaction of radio waves isn't vastly different from the interaction of sound waves (or waves in fluids). But radio receivers are much more specialized than human ears and nervous systems. If could build a radio that could "hear" everything over a wide range of frequencies at the same time, radio reception would be just as chaotic as human hearing can be. It's mostly the fact the fact that "radios" are tuned to specific, isolated frequencies at any given time that makes it seem like the transmissions they're picking up are co-existing more "cooperatively" than they in fact are.

And in that sense, it's still amazing to me that different frequencies whether sound or radio can co-exist as well as they do, without stomping on each other the way they do if on the same frequency.

So, let's look for another analogy.

Imagine if men and women are as they are now for the same gender, but any man and woman could walk through each other and occupy the same space. That'd be analogously amazing.

It's why slightly different frequencies can all travel in the same space and not interfere with other similarly to how the same frequency will that what I think is interesting.

 

[flexy]

I understand what you're saying, but for me, much more fascinating, and in fact almost inconceivable, is the amount of data which comes into my house on one single glas-fiber the size of a hair...

Right now, this one single "hair" with pulsing light inside transfers our entire TV channels (100-200 or so, not sure since we never watch TV), radio channels, phone and then 300MB internet. It's not only the amount of data which comes in through this "hair", also the inconceivable speed it is decoded so it makes for HiDef TV and whatever we do on the internet. Blows my mind. I mean I still remember my first modem (300 baud) where you could literally hear every bit as a tone which was then transferred over the phone line.

Edit: I am aware that a glas-fiber "hair" and then the light serving to transfer data has a higher bandwidth and speed (I guess) compared to a copper line "wire" that transports electricity, but it's still weird to wrap my mind around that all the information is encoded in a pulsing light.

 

[Craig234]

They're two different issues, but I agree - both are amazing. You should have seen 110 baud! You literally could outtype it.

 

[agent00f]

They're two different issues, but I agree - both are amazing. You should have seen 110 baud! You literally could outtype it.

They're actually the same kind of thing. Both are electromagnetic waves, just of different energy levels through a different medium. The main tech diff is details of the transmitters and variations on math in the encoding.

 

[Craig234]

They're actually the same kind of thing. Both are electromagnetic waves, just of different energy levels through a different medium. The main tech diff is details of the transmitters and variations on math in the encoding.

There's a big difference though in a large number of different signals all being in the same space all around you through the air, in contrast to the fast transmission of information over the wire.

Both impressive but different things.