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I amplified my home's Wi-Fi with aluminum foil (jiffchat.com)
447 points by niwde on Dec 26, 2017 | hide | past | web | favorite | 176 comments

It can work surprisingly well, I made a "dish" with an aluminum foil that was able to connect to a Romanian Wi-Fi hotspot from Bulgaria, according to Google Maps it should be something like 20KM distance. I should note that I had direct view of the town as I had significantly higher altitude.

The hotspot was some kind of public service provided by the Romanian town as it's name suggested. The ip WhoIs also confirmed that it was a Romanian one.

Every now and then the connection would have had slowed down and I would do some "Voodoo magic" on the aluminum foil to fix it(Not sure if it was me though, it seemed like if I move the dish slightly or fix a bump in the foil the connection would improve).

This was probably like 7-8 years ago and I was able to get something close to 6-7Mbps as far as I remember.

Old trick is to use Pringles (or other) can as directional antenna: https://www.makeuseof.com/tag/how-to-make-a-wifi-antenna-out...

I used one of these for six months when I moved out of home at 18. I was broke and saving for a wireless connection fee (expensive back in 2005!). When the AP I was using went secure, I'd just point to a different part of the city and repeat.

I remember seeing that in Mr. Robot.

Mr Robot tries to stay as true to hacking as it can.

I've also achieved substantial improvement with simple parabolic shaped, ~40 cm wide aluminum foil constructions, but there always seemed a bit luck involved and it needed some tweaking. Not sure whether the foil mainly acted as shielding that reduces the noise floor from other directions. I've read in other forums that fiddling with aluminum foil is mostly luck because additional reflective surfaces also introduce interferrence patterns unless they are precisely aligned. Even without aluminum foil it often helps to move either receiver or sender by fractions of 12.5 cm (the wavelength of 2.4 Ghz radiation) or of 6.0 cm (in case of 5 Ghz) because the space is basically riddled with interference patterns: https://www.youtube.com/watch?v=aqqEYz38ens

A wok (Chinese stir-fry pan) works surprisingly well for this purpose. It's roughly parabolic, and has a smooth surface that helps you avoid irregularities in the shape of your foil.

It gets even better if you drill a hole in the center and stick an antenna vertically in there. Now you've got a wi-fi antenna with all the advantages of a satellite dish! The Chinese call it wok-fi.

Huh... no kidding. I'm going to have to try that out some day. How was the signal like on the wok with the antenna through the center?

I haven't personally tried sticking an antenna through a wok (just putting one behind the router was enough for my purpose), but rumors say that you can achieve a range of several miles if you do it right.

There are online calculators http://www.radiolabs.com/stations/wifi_calc.html note that the cable loss mentioned is the antenna feeder cable

And Cisco Press do some good books on the basics of WiFi network design.

This seems great for sending but how does it work for receiving? Or did you somehow do this on both ends?

It's not needed to do it in both ends. Naturally, improving both antennas is better than doing in only one, but every improvement in sending is completely equivalent in receiving for a system that uses the same antennas for both directions of communication.

So, if a new antenna in client side improves signal reception by 3dB, it also improves transmitted power by 3dB. If you used the same antenna on the other side, the 3dB would be added again in both reception and transmission, for a total gain of 6dB each direction.

I don't know why people are arguing so much with this when it's straight out of textbook antenna theory. Evidently it's very HN to work things out inaccurately from first principles.

Edit: http://www.cv.nrao.edu/course/astr534/AntennaTheory.html

"An antenna can be treated either as a receiving device, gathering the incoming radiation field and conducting electrical signals to the output terminals, or as a transmitting system, launching electromagnetic waves outward. These two cases are equivalent because of time reversibility: the solutions of Maxwell's equations are valid when time is reversed."

> Evidently it's very HN to work things out inaccurately from first principles.

I find this quite common among people that consider themselves technically minded. One of the key indicators I have for truly 'smart' people is an inclination toward curiosity with new things, and perhaps a degree of humility.

Thanks for the reply. I'm on the move, in my phone, and has regretted on posting the comment as it is hard to elaborate further given the situation.

> It's not needed to do it in both ends. Naturally, improving both antennas is better than doing in only one, but every improvement in sending is completely equivalent in receiving for a system that uses the same antennas for both directions of communication.

Does this actually make sense to you? Gain is a factor; it needs to be multiplied by something. Here's the obvious thought-experiment: consider an (ideal) parabolic mirror in (a vacuum). Put a lightbulb (infinitely tiny) at the focus. Light will come out parallel and will be just as strong no matter how far away the receiver is. i.e. the distance will be irrelevant when the sender is at the focus. Now try reversing their roles, with the lightbulb far away and the receiver at the focus. How strong is the received signal at the focus? You're claiming it won't matter how far away the sender is from the focus, which makes no sense.

Yes, it does make sense to me. I think conclusions drawn from this thought experiment are not entirely correct. Under your experiment when sending you spatially create a beam - there is this beam as wide as parabolic dish and no light anywhere else. With zero interference (using the word quite freely) this beam "will be just as strong no matter how far away the receiver is". With roles reversed, you do not necessarily get directional transmitter. For the sake of argument consider omnidirectional light bulb (the same bulb without parabolic dish) as sender. Classical intro/ELI5 description of transmit power is fixed number of spatially evenly distributed omnidirectional "rays". The larger the distance, the lower number of "rays" you receive per unit of area (receive power scales with surface area of transmit profile, usually r^2). By adding a parabolic dish you effectively increase receive area to size of dish instead of sensor size. When sending, the area over which power is dissipated is constant instead of scaling with distance.

> You're claiming it won't matter how far away the sender is from the focus, which makes no sense.

You are correct in that it makes no sense, but the claim was "every improvement in sending is completely equivalent in receiving for a system that uses the same antennas for both directions", key word improvement. While this is not entirely correct, this approximation (that antenna improvement works both ways equally) is pretty close to reality in practical far field applications.

> With roles reversed, you do not necessarily get directional transmitter.

I don't get why you put "necessarily". You do not, period.

> [...snip...] but the claim was "every improvement in sending is completely equivalent in receiving for a system that uses the same antennas for both directions", key word improvement.

Yes, the claim is wrong:

1. With the sender at the focus and the receiver farther away, the mirror reduces the loss (due to distance, since everything else is assumed ideal as you already acknowledged) to ZERO. You literally cannot do better than reducing your loss to zero.

2. With the receiver at the focus and the sender farther away, the mirror DOES NOT even remotely reduce the loss due to the distance to zero. Loss is still ~1/r^2. Because the mirror only gets so much of the omnidirectional light. This should be very obvious.

I don't care how you slice and dice this, and I'm tired of arguing something this obvious, so I won't keep commenting. 1 is not equal to 1/r^2.

> I'm tired of arguing something this obvious

You're arguing a scenario that is impossible both practically and theoretically and then calling others pedants for pointing out the fundamental flaws in your thought experiment. You're literally arguing against the textbook and then asserting that your thought experiment is close enough to make your point. It might be time for you to stop assuming that everyone else is an idiot and entertain the notion that you might actually be wrong.

The trick here (in this Wi-Fi example) is that the end you control is the end with parabolic antenna - if you can make it to collect enough energy for RX from an omnidirectional source, you can also make it send enough energy towards that source for its antenna to pick it up.

But you're right that "every improvement in sending is completely equivalent in receiving for a system that uses the same antennas for both directions of communication" is wrong; there are different ways of improving TX and RX, even though some overlap a bit, to some extent.

No, as long as antennas and signal power is concerned, I stand by what I said: every improvement in transmission power has a equivalent improvement in receiving power. If you have a more specific doubt, please, feel free to ask.

> If you have a more specific doubt, please, feel free to ask.

Unless by "feel free to ask" you mean "I don't plan to answer", this doesn't really seem like a sincere suggestion. I already did this and you didn't answer.

I'm still on the move, but I'll answer eventually. Your previous post did not contain any questions.

Your thought experiment is not in line with what OP is claiming. You would need to vary the dish size and see how that affects tx/rx.

Have you studied physics and antenna theory?

> Light will come out parallel

No it won't, it's diffraction-limited. The best you can theoretically do is an https://en.wikipedia.org/wiki/Airy_disk

You cannot construct, with any arrangement of mirrors or lasers, a beam that does not diverge.

I'm not going to get into to the "gain wars" (yes, text bok, real-world you can have just one "good" (high gain) antenna, and it will work just fine for send and receive) - but your answer prompts the obvious question: What about lasers? Turns out, before optical lasers there were masers - microwave lasers, bit they were (are?) very limited power:


I was assuming geometric optics... because it was simple enough to get the point across. Which of course you knew, but took the liberty to 'correct' anyway. It's quite impressive how you can always count on HN pedants to deliberately go out of their way to technically-correct you while making sure to completely miss the actual point you're trying to make.

You're the one that started in by trying to wrongly "correct" the statement "every improvement in sending is completely equivalent in receiving for a system that uses the same antennas for both directions of communication" (which is actually correct).

The fact that you can't have perfectly collimated beams and must make do with antenna pattern "lobes" is actually important here.

Think of a parabolic dish on a microphone at a sporting event. The dish blocks noise and interference from the directions you don't want to listen to, and less noise and interference is as useful as if the sender had more power. Same result of better s/n either way.

Or a TV satellite dish. If you were correct, you could rip off the dish and point the antenna forwards instead of backwards, and still watch TV. Not gonna happen.

> The dish blocks noise and interference from the directions you don't want to listen to

You shouldn't need to talk about noise or interference for the argument to make sense. Just imagine there isn't any. The argument yields absurd results either way: the power certainly does depend on how far the sender is from the focus.

You are assuming the mirror is parabolic.

It has been ten years, since I had antenna classes in the uni, so I might be wrong, but I do not completely agree.

Gain is the same in both ends, but my concern about receiving is that gain is applied to everything. This includes interference and noise. So at the receiving end if the SINR is already bad, the antenna gain is not going to help much. This is why you apply the "Low Noise Amplifier" right after the antenna. To make sure that an already bad SINR will not get even worse in the rest of the receiving stages.

I don't know much about radio, so your question had me stumped for a second, and the other replies didn't help me much. Here's my explanation:

Some celestial bodies like the moons of Jupiter, are too dim for us to see, because the amount of light that hits our pupils is too small for our retina to react to. But the light from the moons isn't pointed directly at our pupils, it goes in all directions. If the area of our pupils were twice as large as it is, we would be getting twice as much light from Jupiter's moons — and everything else (except a laser pointed at your eye, please don't point lasers at people's eyes). Telescopes work by being a HUGE pupil, collecting all the light from a wide area and pointing it all right at our pupils (that's not the only thing they do, but it's an important part).

An antenna is like a pupil, and a satellite dish, or this piece of aluminum foil, are like a telescope. Some of the signal from your laptop in the bedroom goes and hits the antenna with a weak signal. A lot more of the signal misses the antenna and hits the foil, and then gets reflected where some more hits the antenna (since the foil was curved, more of the signal hits the antenna on the rebound than on the first pass).

Most antennae are retro directive. Gain is gain.

Are you from Svishtov? Cheers buddy. I did something similar to OMV free wi-fi from my balcony :)

This kind of hack was really popular when wifi was first being adopted. These reflectors work best when they are spaced according to the wavelength. Here is a template I remember seeing years ago:


Yes, I was using this freeantennas antenna few years back. Worked pretty well to extend the range.

t looks neat, but it doesn't tell you how far away you should place it or how big to make it. Am I misssing something?

I'm going to guess that the image is supposed to be printed on a standard-sized piece of printer paper (before laminating). Going to guess "US Letter" 8.5x10" (215.9x279.4mm), but to be certain check the aspect ratio, if it's close to 1.414 then it's probably supposed to be A4 (210x297mm). And make sure that the square prints as a square :)

Then you follow the assembly instructions, which are indeed a bit minimal; The six "bumps" (called "tabs" in the instruction) sticking out the "Windsurfer" part are probably supposed to stick into the six cut-lines of the rounded rectangle piece you cut out from the bottom of the sheet.

This will make the "Windsurfer" part a particular curved shape. I suppose this is the "reflector", so you probably should glue the aluminium foil only to this part.

Then there's the two crosses on the "Windsurfer" part, which you also cut out with a sharp knife, and seem to me to be just the right kind of holes to pierce the whole thing on a wifi-antenna. Get the picture?

Some kind of photo of the finished end-result would have been nice indeed :)

Disclaimer: I know almost nothing about radio signals or antennas etc, the above is just my interpretation of the instructions on the site.

I don't think this is working the way he thinks it does.

What he's likely do is shielding the wifi receiver from co-channel interference, which is likely reducing the noise floor at the AP - which is giving him effectively more range, because now the AP can hear stations that are further away with greater ease.

I don't think this is giving expanded tx coverage lobes as his diagram indicates, its likely a function of lowering the noise floor that gives the extra coverage.

Yeah, some devices can be extremely noisy. If you have a Chromecast or Google Home, for instance, turn Guest Mode off -- it creates a hidden network on the same channel as your AP.

My chromecasts have been acting up really badly recently, I've just gone and disabled guest mode on them all based on this information.

I think sehugg was talking about self noise ie the noise created by the AP's internal electronics

It is unconnected, so it will not dissipate anything (shield). Depending on whether or not it is positioned on a wave node, it will either be a passive reflector or director.

It won't be a satellite dish as the comment thread on the page mentions, though, which is both a passive reflector and a focusing device, whose curvature requires at least some level of precision to be of any help.

For something much more helpful, see http://ham-radio.com/k6sti/wifiyagi.htm

It need not be grounded to be an semi-effective shield, we're talking about frequencies that drywall will attenuate here. Think about it this way, if it can reflect TX, it can also reflect other cochannel signals from that direction.

It may very well be working in more than one mode - but I strongly suspect its a far better shield, than it is a forward power reflector. It also may strongly effect the VSWR of the existing dipoles used here.

A signal from the "correct" direction will have ~half its energy reflected towards the antenna, resulting in gain. A signal from the "wrong" direction will have ~half its energy reflected away from the antenna, resulting in attenuation. It won't shield, though. That requires that you dissipate the signal somewhere.

But to be fair, it's a wild guess. It's a semi-flat piece of foil placed at an angle, at a random distance from 3 individual antennas. That's why I linked to the nice and simple, easy-to-calculate yagi-uda for if you want to hack with antenna gain.

You'd effectively creating a multipath generator with this setup, which means you have the primary signal, then a couple microseconds later, a reflection that is probably 20db under the main signal.

No disagreement that the yagi thing you pointed out would work better.

That said, this is a MIMO router, so that may change the modulus on the multipath problem.

A reflection with just 1 microsecond delay would require a 300 meter reflection path (e.g. 150 meter to/from the reflector). I think you might be thinking of multi-path propagation within the context of long-distance communication (e.g., a HAM QSO).

A regular home Wi-Fi network is already a complex multi-path system, as the primary propagation mode is reflections from walls and ceilings, leading to plenty of self-interference with many hot- and cold-spots from constructive and destructive inteference. We are at most introducing a few stronger reflections in an already extremely reflection-heavy environment. The big question is whether it does any good, either through attenuation or gain.

As for MIMO, I must admit to not knowing much about it—I know it utilizes spacial separation to increase bandwidth, but I do not know much of its actual implementation, and thereby weaknesses.

Yeah, something so imprecise isn't likely to work as he thinks. Proper shielding can do a lot more. If you made your house/apartment a Faraday cage and eliminated neighbors' AP's that would already solve most problems.

> If you made your house/apartment a Faraday cage

Might put a crimp on your cell phone reception ...

Is there a way to build your Faraday cage to block out wifi wavelengths but not cell phone ones? How far apart are they?

You could likely block anything over 2.3 GHz and get away with it: https://en.wikipedia.org/wiki/Cellular_frequencies_in_the_US

unless you have Sprint ;-)

This is usually done with a femtocell.

[0] https://www.att.com/att/microcell/

I've always wondered what it would be like to have paint like this as an exterior primer

https://www.lessemf.com/paint.html (Warning: this site gets a little silly)

Just move to the 5.8ghz band. There's an extra 50MHz of bandwidth available and these frequencies are much more strongly attenuated by walls. There's also usually much less interference from other unlicensed equipment like cordless phones, baby monitors and microwave ovens, although you can occasionally get hosed by a dodgy Chinese video sender operating at well above the legal limit.

You might need to replace a couple of older pieces of equipment, but it's a hell of a lot cheaper than turning your house into a Faraday cage.

I can see this working well, unless LoS goes through one of those walls. There's a metal mesh in most of the walls of my house (putting two routers directly opposite each other on either side of an internal wall will cut the signal strength to about 60%), and trying to get a reliable signal because of the shape of the house (roughly L-shaped) was a nightmare (line of sight was through two external walls).

Will changing the Channel help in this case?

doing a proper site survey and changing channel would help - you need to see what channels interfere in each quadrant of the building, and then choose accordingly. You're also generally better off on a channel with one moderately strong cochannel station, than 10 weak cochannel stations.

If you want to to do this "properly", see http://ham-radio.com/k6sti/wifiyagi.htm

When messing with antennas, things like distance needs to be thoroughly calculated. Foil can help in many ways, but it can also make things worse—antenna calculations are tricky.

Done wrong this will increase reflected energy at the feed point and make the transceiver run hotter than it is supposed to, possibly leading to an early failure. Measuring SWR at 2.4/5 GHz requires some expensive instruments; note that the link you provided has only "calculated" SWR, not measured. Wifi doesn't involve much power, but these low cost Wifi transceivers are engineered with rather limited headroom for reflected energy and shipped with antennas that work within those limits, so if you do this you're a test pilot; there is no complaining if it lunches itself.

As long as you're not running a high-power transceiver (i.e. not consumer gear or consumer gear out of legal spec), I would not be worrying about SWR problems. Consumer Wi-Fi chipsets are designed to be fairly rugged. They normally operate nowhere near their limits.

> antenna calculations are tricky.

Especially at high frequencies. One of the first things I did when I got access to a computer as a kid was to write an antenna calculation program for Yagi antennae.

Impressive gain by the way, a factor of 8 (almost 9 dB) from that super simple mod.

This particular example of yagi for wifi - what's the logic to customize it for my router ?

In short, I'm looking for logic to repeat this for my router's dipole antenna and possibly with custom wires (not #14 or paperclips of unknown thickness mentioned there)

As you already have a working dipole (which you have in this case), the primary thing to consider is the element lengths and spacings. If you don't have one of those routers with massive (and empty!) plastic antennas, there's probably a good chance that you can use the authors design parameters.

Otherwise, there's plenty of 3-element Yagi-Uda calculators online where you can stuff in various amounts of parameters and get the unknowns—the author used fancy antenna simulation software, but you don't need that.

A few links:



Thank you, arghwhat

Does anyone know what program the author is using? It looks interesting.

I don't know that specific one, but there is plenty antenna simulation/modeler/optimizer software out there.

I know what some of those words mean...

When we were kids we took massive mesh wire frames and wrapped them around the receivers of these kind [1] of dinky walkie talkies. It fully extended the range by a whole two blocks. We thought we'd invented sliced bread.

[1] https://img.segundamano.mx/medium/32/3227658794.jpg

Wow, I had the exact same set of walkie talkies as a kid! That image certainly brought back some memories! :)

Do not tilt the antenna though. Maximum emission of an dipole is perpendicular to its axis.

On occasion, going against the grain (in case of interference from another transmitter) can help if you can polarize the signal somehow.


Of course you'd have to do the same thing at the receiver.

you can for point to point use multiple ap with anteneas using differently polarised antenas - to increase the bandwidth

That seems intuitive and useful.

I was thinking of doing something similar a few days ago but came to the conclusion — perhaps wrongly — that the inevitable creases in a DIY aluminium foil sheet would render it ineffective as a dish, due to the scatter created.

Anyone more knowledgeable able to chime-in on the effect of creases here? I couldn’t find any mention of it in the article...

speed of light / 5 GHz / 4 ~= 1.5 cm.

If you can keep the size of the largest crease/feature/defect in your foil smaller than this, you should be okay.

I've seen microwave focusing mirrors for high-power applications that were rough CNC milled surfaces. The overall shape had been optimized fairly precisely by simulation, but because the intended wavelength was so long, the tool marks were irrelevant.

To get some intuition of why quarter wavelengths seem to come up a lot here, it's helpful to imagine a long transmission line carrying your signal. What would happen if you were to add a quarter wavelength stub to this transmission line?

So something like:

  Source ----------------------------------- Dest
                         | lambda/4
                         |   stub
The transmission line carries an electrical current proportional to the signal from "Source" to "Dest." When the current gets to the stub, you can think of it as going down two paths -- continuing to Dest, as well as down the stub. When the current component going down the stub gets to the end of the stub, it reflects and travels back up the stub (reflection coefficient of the "open circuit" at the end of the stub is 1).

By the time the reflection gets back to the transmission line, you have a phase offset of half a wavelength relative to original signal on the transmission line. If you add two signals that are half a wavelength apart, they combine destructively (cancel each other out). So the quarter wave stub acts like a very basic filter, and you actually won't see much of your signal at "Dest" when your transmission line has a quarter-wave stub like this.

Microwave engineers use all sorts of tricks involving transmission line segments that are a quarter wavelength long. So when you're trying to build an antenna (e.g. out of foil, or if you're adding metal support structures to a large antenna), it's helpful to use the heuristic: "if you need to add features that are not part of the original design, try to keep them smaller than a quarter wavelength."

blackguardx is right that restricting the maximum feature size to 1/10 of the wavelength is probably a better rule of thumb if you want good performance. If you can get it down to say, 1/2 of a quarter wavelength (1/8 wavelength), there's a reasonable chance it'll still work.

Wow, thanks for this — I did HS-physics but much of my knowledge has since left me... :)

Would love to dig into the science behind this a bit more — I don't really know where to start — i.e. why you're dividing by four.

So as not to waste your time, is there a named phenomenon that you can link me to to learn more about this?

Thanks again!

As a quick off-the-top-of-my-head calculation, I take 300,000,000, the speed of light in meters/second (approximate), divide by cycles per second, you get wavelength in meters. In this case, parent calculates a quarter wavelength. A full wavelength is about 5.9cm. It’s easy to get off by an order magnitude in your head, but if through sheer repetition you know 28Mhz is about 10m, you’ll know you’re off if your 30Mhz calculation gives you 0.98m. And you can do the math from there to figure out that 14Mhz is about 20m, etc. Do it enough and you can mentally move some decimal points in your head to get a pretty good approximation for about any frequency. I learned it at some point fiddling with amateur radio, but here’s a page that I think explains it well: http://www.digitalairwireless.com/wireless-blog/t-5ghz/calcu...

300 000 000 m/s

Yeesh, it’s right there in the article I linked, innit? Fixed, thanks.

It has to do with quarter wavelength features making good antennas.

I would say that you want to be less than 1/10 of the wavelength to minimize the effect though.

Antennas are usually built to 1/2 or 1/4th the size of the wavelength. I'd imagine that's why - but am curious myself if it is something else. It's the only 1/4th fraction that comes to mind.

I don't know if there's a specific name for it, but a quarter wavelength shows up as an important feature size in a bunch of RF (and acoustic) formulas. The exact physical reasons seem to vary by context.

I would also like to know this. I don't know if there's a save function in h.news or not so leaving a comment

If you click through to the comment, you can "favorite" it and then it shows up in https://news.ycombinator.com/favorites?id=dukes_haven&commen... which you can also find on your profile page under "favorite comments".

Wow. I'm one of today's lucky 10,000. Thanks!

It will dissapear more slowly here: http://handlr.sapico.me/Home/ByTag?Name=diy :p ( unfinished webapp)

Could you tell me where the /4 comes from, please?

Quarter wavelength. Waves will flow around something smaller than 1/4 of their wavelength almost without interruption.

Thanks. Could you point me in the direction of some reading material?

That has the look of a rule of thumb, which as a civil engineer that ended up in IT, sounds a bit familiar.

I've heard good stuff about the ARRL antenna book, although it's pretty large and spendy.

It’s always fun when you get to use the speed of light in a commonplace application!

it's really speed of radio.

creases could help scatter the signal into more directions and maybe change the signal properties so it's easier to go though some materials. I know nothing about radio but creases makes sound more even (lookup Diffusion) if it's random because it doesn't strengthen any particular wavelength, and sound bounces in different directions instead of straight.

Most of the DIY's I've seen on this use aluminum cans. You could try that.

Pringles cans were really effective for me

I got this guy and this allows me to read / play games in my bathtub


How is this only $6? It looks great.

Is there a way to see the tangible output of the coverage?

How is the author drawing those diagrams? Can I map my room with the strength of wifi signals at different points?

I want to do these small hacks but also want to see the change validated in some way. Any pointers will be appreciated.

Slight nit there's no amplification here just focusing to make the field more directional.

Gain is effectively the same as amplification, any kind of gain achieved in a passive manner indicates some kind of directional compromise.

It also should work equally well when receiving and transmitting, whereas an amplifier would work for only one direction (so you'd need two, one to output more power, another to amplify the received signal).

But technically there are legal maximum emitted powers unless you are "a professional"

Fortunately the legal maximum is total radiated power and not 'power radiated in one particular direction'.

I did some pretty interesting stuff with 19 element Yagi's and very low power transmitters.

I am using my neighbors WiFi, which I can only catch in my balcony. He stays above me, but diagonally opposite, so the source is quite away. Any way I can amplify the WiFi strength? So I need the source to be around in order to amplify?

Why not consider putting a good extender placed near your balcony?

I use one at my Dad's house (next door to mine) so that I can access my wifi. Our houses are brick, and in spite of that, the extender I got does a pretty good job. I've tried various extenders in the past few years, and they were all pretty flaky, but the latest generation of extenders seems to perform much better than older ones.

I'm using the Wirecutter's current favorite, the TP-Link RE450. Having said that, the RE450 was recently found to be spamming NTP servers with an excessive amount of requests.

You could buy a cheap TP-Link Router with a USB-Port and LEDE/OpenWRT support, add a second wifi interface (usb dongle) and then use your neighbors wifi as WAN connection.

Good usb dongles are: 1. Alfa AWUS036NHA – $28.97 2. TP-LINK TP-WN722N OR TP-WN722NC $15.99

Benefits: have "your" wifi on a separate channel, you have your own subnet, firewalled (nat) from your neighbor's net.

I second ce4's suggestion. LEDE/OpenWRT are open source projects of linux based firmwares that run on embedded devices. Tangentally, I've used OpenWRT in combination with: a cheap router, a USB dongle as a second wifi interface, a 4G/LTE hotspot and a package called MWAN3 (previously MultiWAN) to configure a cheap and reliable setup for automated WAN failover (backup internet) and for circumventing restrictions of 4G/LTE hotspot devices.

Lookup cantenna which was popular back in the day for catching WiFi from further away spots.

Saw a vid on youtube where a guy uses a metal kitchen strainer as a dish antenna for his laptop wifi out in the middle of farm field. The 'available networks' list shrinks and grows as he points it in various directions.

Would you kindly post link to that video?

First thing that crossed my mind.

Use a Ubiquiti Nanostation directional antenna. These things are quite powerful and relatively cheap. Have used them before to link two sites ~20m apart.

Seconding the Ubiquiti rec, just in general. Their equipment is better in difficult radio environments than anything else I've ever used.

Thirded. I had some Meraki (MR32 and MR18) equipment in my house and spent years mucking with the settings and always felt like something was wrong. My AP-AC-PRO Ubiquiti APs that replaced them have astoundingly better range and throughput. IMO the Meraki APs are worse than consumer gear in terms of range.

The repeater suggestion is exactly what I did at university. There was a network I could _just_ pick up most of the time on my laptop that I wanted to use (run by the central university rather than my college so it had fewer usage limits). Putting a DD-WRT router by my window which connected to it as a client, then shared the connection over Ethernet, got me a rock solid connection.

It also lets you put your devices on their own subnet/NAT, which is nice from a security perspective (I've do this at home quite a lot - re-purposed router connects the main network on 2.4GHz and treats it as a WAN, then provides its own connections on 5GHz).

I think the source needs to be strong. I'm currently using a wifi extender and noticed the speed isn't good when I move the extender to a room further from the source.

That is because range extenders just rebroadcast so you cut your bandwidth in half with every hop

What´s the 'household shelter' for?

Mandatory in Singapore houses. Practically used for live-in maid or general storage. But effectively involves a massive metal box in the middle of your house. Given the information (a.o. Sunlight as a electrical contractor) in the blog the OP is living in Singapore.

The red circle in his first image will like be much more distorted in practice by the bomb shelter, meaning his home WiFi will have a lot of trouble reaching whats behind the shelter (i.e. the bathroom and the Mr Bedroom in particular). Basically he got a pretty horrible spot for his router. Study/bedroom3 would have been substantial better.

some countries mandate civil defense shelters in private dwellings, switzerland and singapore both come to mind.

Swiss law does not require shelters in all private dwellings, (you can pay a small amount at the time of construction for a place in a communal shelter) and I'm not sure that even that is required any more.

Large public buildings maybe still need shelters by law.

I have done that before except I went to HD and bought some aluminum flashing and made a corner reflector. Worked really, well and looked a bit ... tidier.

Put 'em just behind the antenna like a dish aimed toward where you want to bend the signal to. It's not great, but it's cheap and easy.

Have you tried something similar before? Does it work?

When I had my WiFi router in the basement I placed it in an aluminum oven dish, so that the reflection went towards the ground floor. It was a small but noticeable improvement.

I have, it is hit and miss. But was enough pf a hit to stay in use for over a year back in the 802.11b days. Grounding the reflector should also help iirc.

I am using my neighbors WiFi, which I can only catch in my balcony. He stays above me, but diagonally opposite, so the source is quite away. Any way I can amplify the WiFi strength? So I need the source to be around in order to amplify?

You can put the dish on either end, although if you don't have some sort of external wifi antenna, it'll be trickier

Aha I did something similar to this a while back. Had an ancient computer with a $2 WiFi dongle very far from the access point.

It could barely sustain a connection, never mind actually doing anything. So I cut up the neck of a bottle, covered with aluminium foil, and even added a little reciever at the focus point of the dish.

Signal bars went to a solid usable III.

For optimal results, place the reflector at distance d = c / 2f behind the antenna (half wavelength). Where c is the speed of light and f is the frequency of your wifi. For example, for 5 Ghertz signal, that will be 30mm.

How exactly does this work? Especially in the case of a signal which isn't a perfect sine Wifi where (AFAIK) 5Ghz is merely the frequency of the carrier which is then modulated or so? Or maybe it's like 'close enough'?

Reminds me of this guy who used the same technique on the receiver: https://youtu.be/VZKc3PBs67c

For the antenna case (and I believe for the optics case too, but I'm not an optics guy) the beam disperses as 1/r^2 in both cases.

In transmit , the reflector provides focusing, which puts more power in less of the volume. In receive, the increased aperture allows the antenna to capture a greater area of the incoming wave giving more receive power. The effects are equal and usually just thought of as"gain" which is reciprocal for transmit and receive.

better off just getting some patch antennas and using them.. though that's more expensive then foil, it does give you better control of the directions.

See also: http://mentalfloss.com/article/515193/researchers-develop-ch... ("Researchers Develop a Cheap Way to Improve Wi-Fi Coverage With Aluminum Foil")

This blog is missing a lot of details before we can consider this experiment successful. Most importantly, what is the usable throughput of a station in the "improved" coverage area? I would recommend using iperf before/after to see if there is any practical benefit.

Did that a while ago, when the trees have leaves, I hardly receive WiFi in my shed. So I put a aluminum foil when I went to the back around the router.

It worked, but other directions are difficult. I also had success by changing the channel with less interference in my router settings.

Just keep in mind you need some antenna diversity for the MIMO to work. Adding the foil increases the directivity, which you don’t want for MIMO. Though it improves fringe reception, it may reduce the data rate for devices that already have sufficient SNR.

The geek in me loves stuff like this. The old and jaded techie in me says just get something designed to solve the issue like:

https://eero.com or the UniFi Mesh


From eero’s site: “From the window to the wall” — using pop culture references is risky when you don’t understand them.

Skeet skeet skeet.

The jaded geek in me says just run some ethernet this WiFi is too much hassle

Yeah, but lots of devices people might want to use on their home network are inconvenient to tie to ethernet. There's a good case to be made to wiring what can be wired, though.

The consumer and frugal shopper in me sees the $400 price point, and doesn't think it compares favorable with a few dollars worth of aluminum foil.

Beware cheaping out on wifi kit I have bitter experiance of trying to use POS dlink kit to provide wifi in our new office.

But for home use multiple AP's with powerline to connect them is actualy a simpler solution than mesh as using wifi for the DS (distribution system ) is always going to be slower than a wired.

I agree, and I have multiple through a wired back end, but due to very congested spectrum usage in my neighborhood, I I have less than stellar reception at certain times in my home office (a walk in closet with no physical network hookups) which is about 30 feet over and up a floor from the closest AP. A little coaxing of the waves might go a long way for me.

It's a little bit a shame, that this is not a standard solution for most IT related people, wouldn't you say?

I just got back home for the holidays and made fun of my dad for doing this. Seems like it is working tho!

theoretically, are there any regulatory issues on a piece of aluminum sold (and marketed) for this purpose?

if not, why aren't there cheap and effective such designs on alibaba - why have to DIY?

No regulatory issues. The aluminum acts to increase the antenna gain (i.e. concentrate the signal in a particular direction). The total power does not increase instead you take some from one place and add it to another.

There are tons of products for sale. You can get a replacement antenna that is a directional dish for example, instead of the typical omnidirectional dipole (stick).

> No regulatory issues. The aluminum acts to increase the antenna gain (i.e. concentrate the signal in a particular direction).

AFAIK, many countries limit the EIRP, which increases with the antenna gain.

Correct. In the US, for example, for 2.4 GHz point-to-multipoint, EIRP is limited to 4 watts, and maximum power to the antenna is limited to 1 watt. So, if your router does 1 watt, you are limited to a maximum 6 dBi antenna gain. Lower the router power, and you can use higher gain antennas.

It's more complicated for 2.4 GHz point-to-point. At 1 watt transmitter power you are allowed a 6 dBi antenna. But for every 1 dBi you reduce transmitter power, you are allowed an additional 3 dBI of antenna gain to a maximum of 30 dBi antenna gain at 160 mW transmitter power.

5 GHz has even more complicated rules, I believe.

See: https://www.air802.com/fcc-rules-and-regulations.html

Or if you get your ham license you have a limit of 1500W PEP[1], just plug your callsign into the router ID and away you go. However that means you're also subject to no encryption or business related traffic.

[1] http://www.qsl.net/kb9mwr/projects/wireless/allocations.html

>However that means you're also subject to no encryption or business related traffic.

how does that work? isn't all wifi traffic encrypted by something between devices and AP?

(I skimmed your link and did a find for encry on it but saw nothing.)

No, encryption is an optional feature of the 802.11 standards. Every once in a while I see an unencrypted wifi AP nearby (it's the default on Android to show a notification whenever it sees an unencrypted wifi AP).

I think 4W that is for professional ptp use only.

This was interesting, thank you. Given that we're literally talking about a piece of aluminum foil, I'm surprised this isn't more common.

I've heard it works for 802.11n. Does it work for 802.11ac?

It has an effect, but much smaller than hoped in my experience

This is called Beamforming. Look it up.

does this stuff work with walls?

I have a basement with thick walls.

It would mostly depend on what is in the walls

Bricks and concrete, I guess

A bit off topic, but what is this page doing, loading almost 500K in 2 XHR calls for approximately 9K of text... Egads, all the images are inlined data URIs!

I was staring at a blank page with a single image for over 10 seconds before the article text loaded. No loading indicator or anything.

Thanks, I tried multiple browsers before I read your comment. It took 30s for me.

There's no reason for this content to use JavaScript at all. I'm going to start holding this up as an example of why browsers shouldn't have JavaScript at all - many developers simply don't understand when not to use it. Educating them one at a time won't fix it.

> There's no reason for this content to use JavaScript at all.

How else would you add live comments without JS? This page is effectively a big chatroom. You can write at the bottom of the page and the website fetches the new messages async.

Don't tell me you would have a big http refresh every 5 seconds to load in the new chat messages, that's even worst than using JS.

>How else would you add live comments without JS? This page is effectively a big chatroom. You can write at the bottom of the page and the website fetches the new messages async.

Why on Earth does it need to be some kind of live chatroom? Just render them server-side and add live updates as a nice-to-have if JavaScript is enabled.

> Why on Earth does it need to be some kind of live chatroom?

Well, the website is called jiffchat.com and is a collection of chatrooms.

That being said, I turned off JavaScript and you are right. The page gets stuck on a lazyload placeholder. The initial content should be loaded and only the chat part be should added by JS.

This is why I uploaded this as an image: https://i.imgur.com/gSLrqPl.jpg

I hate sites that require JS and are not viewable on archive.is or Wayback Machine.

took about 2 seconds for me but yeah, it almost feels like they are using huge web fonts with no default local fonts... (probably not the case because I usually disable web fonts)

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