What If You Could See WiFi? • Hacker News Board

Re: What If You Could See WiFi?

#41

Post by noonespecial » Wed, Jul 24, 2013, 4:06 AM UTC

Ackley wrote: post #35

noonespecial wrote: post #2

Illustrations like these do more harm than good. It lets people imagine that spaces are getting 'flooded' with 'stuff'. Radio is a light. A blinking light. A transmitting antenna like a light bulb. If your receiver can see the light blink (or a reflection of it) the signal gets through. Radio has the added benefit that (especially at longer wavelengths) most of the material world appears to be made of tissue paper.

Where do you think interferences come from?

Imagine that frequency is color (actually true). Tuning is searching for that color. So you, the receiver, are tasked with finding a (for example) blue light and counting the blinks. Easy until you surround that blinking blue light with 1000 more just like it all blinking at different speeds. Complete the metaphor with the fact that directionality is hard or often impractical so imagine your field of focus is slightly blurred, like looking through the viewfinder of a camera that isn't focused. All that other blue light is interference.

There are only 11 or so distinct "colors" in 802.11g and some of them are close to each other and quite hard to tell apart.

Re: What If You Could See WiFi?

#42

Post by lcedp » Wed, Jul 24, 2013, 2:04 PM UTC

sp332 wrote: post #38

lcedp wrote: post #37

Earlier quoted context omitted.

Ok, point taken. It is vaguely a logarithm function. But what's the base of this logarithm? How much is it curved? Just try light up a big room which has no windows with a candle - you can see pretty well at the distance of your hand, but in a few meters from you - it's plain darkness. I expect wi-fi waves to be like this. Using the grath "Perceived Brightness" at [1] we have roughly the following table: Distance/Act…

Luminous efficacy depends on wavelength, with the eye being most sensitive to 555nm (green) light at 683 lumens/Watt. Most wifi setups max out at 1W (I think?), so if the eye were as sensitive to wifi signals as to green light, we could get 683 lumens which is about the same as a 60W incandescent bulb.

And?

Re: What If You Could See WiFi?

#43

Post by sp332 » Wed, Jul 24, 2013, 2:25 PM UTC

lcedp wrote: post #42

sp332 wrote: post #38

Earlier quoted context omitted.

Luminous efficacy depends on wavelength, with the eye being most sensitive to 555nm (green) light at 683 lumens/Watt. Most wifi setups max out at 1W (I think?), so if the eye were as sensitive to wifi signals as to green light, we could get 683 lumens which is about the same as a 60W incandescent bulb.

And?

Oh, so if we're trying to imagine how bright a wifi router's "light output" would look if we could see it, we can just imagine a 60W (monchromatic, say green) lightbulb. Of course the light would pass through walls more easily which is a bit unusual :) But for attenuation over free space, I think the analogy to a 60W light bulb is very useful.

Re: What If You Could See WiFi?

#44

Post by somesay » Thu, Jul 25, 2013, 2:23 PM UTC

toyg wrote: post #23

noonespecial wrote: post #2

Illustrations like these do more harm than good. It lets people imagine that spaces are getting 'flooded' with 'stuff'. Radio is a light. A blinking light. A transmitting antenna like a light bulb. If your receiver can see the light blink (or a reflection of it) the signal gets through. Radio has the added benefit that (especially at longer wavelengths) most of the material world appears to be made of tissue paper.

Well, radio pollution is still under debate. In Italy they've supposedly found significant discrepancies in cancer distribution near large radio transmitters (i.e. higher rates of cancer). We're talking humongous power and extreme proximity though, nothing like wifi.

That's actually the reason why people who are blocking new transmitters are somehow dumb. Less transmitters means higher peaks for people near one. Still you have to be cautious what studies you believe.