
I amplified my home's Wi-Fi with aluminum foil - niwde
https://www.jiffchat.com/m/2ZUaCkOed9+sHn4FHOS+PC2TGvE_vfjTVtKvyYvWbAE=
======
mrtksn
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.

~~~
throwaway613834
This seems great for sending but how does it work for receiving? Or did you
somehow do this on both ends?

~~~
aylons
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.

~~~
throwaway613834
> 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.

~~~
pjc50
> 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](https://en.wikipedia.org/wiki/Airy_disk)

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

~~~
throwaway613834
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.

~~~
pjc50
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.

------
hallz
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:

[http://www.freeantennas.com/projects/template2/](http://www.freeantennas.com/projects/template2/)

~~~
Toast_25
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?

~~~
tripzilch
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.

------
Aloha
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.

~~~
pishpash
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.

~~~
B1FF_PSUVM
> If you made your house/apartment a Faraday cage

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

~~~
komali2
Is there a way to build your Faraday cage to block out wifi wavelengths but
not cell phone ones? How far apart are they?

~~~
bitdivision
You could likely block anything over 2.3 GHz and get away with it:
[https://en.wikipedia.org/wiki/Cellular_frequencies_in_the_US](https://en.wikipedia.org/wiki/Cellular_frequencies_in_the_US)

~~~
Aloha
unless you have Sprint ;-)

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

~~~
topspin
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.

~~~
arghwhat
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.

------
arxpoetica
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](https://img.segundamano.mx/medium/32/3227658794.jpg)

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

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

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

[https://en.wikipedia.org/wiki/Dipole_antenna](https://en.wikipedia.org/wiki/Dipole_antenna)

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

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

------
sarreph
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...

~~~
ohazi
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.

~~~
sarreph
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!

~~~
dukes_haven
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

~~~
sp332
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...](https://news.ycombinator.com/favorites?id=dukes_haven&comments=t)
which you can also find on your profile page under "favorite comments".

~~~
j1elo
Wow. I'm one of today's lucky 10,000. Thanks!

------
desireco42
I got this guy and this allows me to read / play games in my bathtub

[https://www.aliexpress.com/item/Original-Portable-Light-
Weig...](https://www.aliexpress.com/item/Original-Portable-Light-Weight-
Xiaomi-Mi-WiFi-300M-Amplifier-2-Expander-for-Mi-Router/32789948233.html)

~~~
snowpanda
How is this only $6? It looks great.

------
aryamaan
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.

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

~~~
jacquesm
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).

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

~~~
jacquesm
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.

------
godelmachine
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?

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

~~~
ourmandave
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.

~~~
godelmachine
Would you kindly post link to that video?

------
joniels
What´s the 'household shelter' for?

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

~~~
hopscotch
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.

------
JustSomeNobody
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.

------
kleer001
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.

~~~
niwde
Have you tried something similar before? Does it work?

~~~
bonzini
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.

------
libeclipse
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.

------
SagelyGuru
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.

~~~
stinos
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'?

------
Nux
Reminds me of this guy who used the same technique on the receiver:
[https://youtu.be/VZKc3PBs67c](https://youtu.be/VZKc3PBs67c)

------
lpmay
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.

------
aknfo1341
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.

------
fulafel
See also: [http://mentalfloss.com/article/515193/researchers-develop-
ch...](http://mentalfloss.com/article/515193/researchers-develop-cheap-way-
improve-wi-fi-coverage-aluminum-foil) ("Researchers Develop a Cheap Way to
Improve Wi-Fi Coverage With Aluminum Foil")

------
presto8
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.

------
NicoJuicy
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.

------
madengr
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.

------
myrandomcomment
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](https://eero.com) or the UniFi Mesh

:)

~~~
city41
From eero’s site: “From the window to the wall” — using pop culture references
is risky when you don’t understand them.

~~~
dmourati
Skeet skeet skeet.

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

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

------
logicallee
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?

~~~
ars
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).

~~~
cesarb
> 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.

~~~
tzs
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](https://www.air802.com/fcc-rules-and-regulations.html)

~~~
vvanders
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](http://www.qsl.net/kb9mwr/projects/wireless/allocations.html)

~~~
logicallee
>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.)

~~~
cesarb
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).

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

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

------
yarg
[https://www.youtube.com/watch?v=LY8Wi7XRXCA](https://www.youtube.com/watch?v=LY8Wi7XRXCA)

------
doomjunky
This is called Beamforming. Look it up.

------
k__
does this stuff work with walls?

I have a basement with thick walls.

~~~
elliottcarlson
It would mostly depend on what is in the walls

~~~
k__
Bricks and concrete, I guess

------
pimlottc
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.

~~~
Sir_Cmpwn
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.

~~~
Raphmedia
> 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.

~~~
Sir_Cmpwn
>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.

~~~
Raphmedia
> 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.

