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Antenna hacking wireless routers – Joe

SUMMARY: Antenna hacking greatly improves wireless up-time.

As the world increasingly goes wireless, users increasingly confront the vagaries of bouncing signals around homes and offices. Having installed a wireless router at home, I was confronted with the problem of ensuring an adequate and stable signal from one end of the house to the other – and so the Great Antenna Search begins.

In the beginning, there was the Netgear wireless router (MR814v2); this is the “B” version, which means it tops out at a data transfer rate of 11 Mbps. These are now old hat, as the industry now goes to “G”, which tops out at 54 Mbps. There are also products that double that – 108 Mbps. This begs the question of who needs these blazing speeds (Netgear: “Great for all your heavy bandwidth applications like video streaming, multi-player gaming and MP3 downloading”), but let’s accept that you need a wireless connection.

Now all this is great, except that getting the signal from the router to your laptop and back is more of a challenge than you might expect. Here is where the antenna part comes in (let me state at the outset I am NOT an expert – readers with more experience on this issue are more than welcome to chime in); This is one time more is better.

It turns out, for the Netgear wireless routers, that the antennas are pretty limited; the “B” version data sheet states “Antenna: 2 dBi”. The “G” version must be better – right? Its data sheet states “Antenna: 2 dBi attached”.

I had the luxury of testing both the “B” and “G” versions with my laptop and could find no discernible difference between them – I could not get a consistent signal about 50′ from the wireless router. Half the time the signal would be “Very Low” (the last bar to “No Signal”) and half the time “No Signal”. At this distance, I would get speeds of something like 1 to 1.5 Mbps – the cable connection I have will do something like 6 Mbps straight out of the cable modem.

In the path between the router and laptop there are three walls (plaster, not wallboard – makes a difference), a kitchen, TV and wireless phone. I guess this must be a signal black hole. When you read the advertising literature on lots of wireless routers, you may see something like “range up to 300 feet”. HA! the key phrase “up to” is the ad copy writer’s “Get Out of Jail Free” card – this means anything from 0 to 300 feet is OK.

In the real world, you can get a 300 foot signal in an open field in an Iowa corn field, no wind blowing, sun spots at low ebb and no other antenna in sight for 100 miles. Anyplace else is a crap shoot, like my house. Not to mention that at 300 feet, the signal is so low that your transmission rare is probably something like 100 Kbps.

So here you are with this great wireless router that puts out a puny signal. The obvious hack is to boost antenna gain¹ (the signal) so you can realize something close to performance you expected. Only there’s one problem with the Netgear routers – the antenna is NOT removable. I took the Netgear apart and found this:

Inside

The antenna mount has a small knob that holds it in place – no doubt it can be easily removed….

Net Ant

but it’s soldered in place:

Solder

I’m sure this can be hacked (cut the cable, separate the braid from the internal wire and go at it), but a project for another day.
{mospagebreak}

¹ I’m not going to get into what gain, or dbi, is – if you’re interested, go HERE for a basic discussion.

There are a couple of wireless routers where antennas are removable – Linksys is one of them and I decided to buy a “B” version (BEFW1154) because a) I don’t need huge file transfer speeds and b) it’s cheap.

I also knew, from a Radio Shack visit, that 5.5 dbi antennas are available for it, so I purchased a pair to try out:

Ducks

The stock antenna below and the Radio Shack replacement above.

What I found with the Radio Shack antennas is that in my signal black hole, I now could get a fairly consistent “Very Low” signal with a “No Signal” about 10% of the time; I achieved speeds of about 4 Mbps – a definite step up from the Netgear experience.

Now being of curious mind, I started on an antenna quest. Doing a Google on “2.4 ghz antennas” brings up a wealth of possibilities. After feeling a bit overwhelmed, I started to think about what I wanted to achieve. One thing I did not want to do is broadcast a stronger signal all over the neighborhood, so I decided to go for a directional antenna rather than omni-directional (the latter broadcasts a signal over a 360 degree footprint).

The “rubber ducky” antennas are omnis, so whatever gain you have will be distributed over a wide area. A “flat patch” antenna is one where the signal is directional, which means you orient the antenna towards the laptop. With this type antenna, your neighbor is out of luck (unless he’s in your line of sight).

I decided to buy a Hyperlink 2.4 GHz 11 dBi Dual Cable Dual Diversity Flat Patch Antenna.

Hlink

Pic courtesy of Hyperlink.


{mospagebreak}

Now some explanations: the Linksys features two antennas – this is because this router looks at signals from both antennas and picks the strongest one (this is the “dual diversity” part). Figuring that rather than use only one of the antenna ports (apparently it’s possible – I believe the right hand antenna is both receive and transmit while the left is receive only), I elected to stay with an antenna that uses both ports.

Note that the connector is of a special type called an RP-TNC Connector – this is supposed to discourage antenna tinkering as it’s a less common connector. I don’t know how well this strategy works, as I found lots of products with this type connector.

I now had to build a stand for the router and antenna:

Flat

It’s a simple affair, but does the job.

After doing some orienting, I know have a connection that is “Low” all the time, compared to the “Very Low” 90% of the time I had before; the flat patch is a definite improvement over the Radio Shack rubber duckies. I’m still getting 4 Mbps download speeds, so I did not see any appreciable performance boost.

CONCLUSIONS

I’m sure there are lots of users who have great wireless performance in their homes, as well as I’m sure there are a number of frustrated people expecting more. Replacing antennas is probably the easiest way to get performance you expected. I’d more than welcome feedback on this from more experienced readers.

For a view of antenna possibilities, the HyperGain ® 2.4 GHz In-Building Antennas features a good product range to get the juices flowing.

DIY Projects CONTINUED page 4…

Email Joe

As usual, our great readers chimed in with tips and experiences to share. Many readers provided links to sites that feature…

“DIY” Antennas

Stan Swan

It’s our experience that even simple commercial external antenna are VERY COSTLY – often multiples of the basic high tech WiFi electronics! Given the cussed connectors many APs & cards have, an approach has been to simply enhance the performance of the existing antenna with suitably curved reflectors behind the antenna.

In other words, bring more signal to the existing antenna.

This of course is our USB WiFi “scoop” approach, but we “thought big” for field work & also wanted the swap out convenience of USB devices.

Ref

Pic courtesy of Stan Swan.

One of the simplest DIY I’ve seen just used cardboard/glued on foil, or 5mm mesh, & a polystyrene template to hold the setup over the APs rubber ducky for > 6dB gain & cost almost nothing! Even a classic corner antenna, made from a piece of aluminium (empty beer can or juice carton with metallised interior ?) may double range. Construction details
HERE and
HERE.

Grey

I’m sure that I’m not the only one to point this out, but a couple of things I thought I’d share. http://www.freeantennas.com has some templates you can use for some free antennas. Now that you’ve tried the commercial antenna, try dropping one of these babies on your stock and rubber ducky antennas to see what happens.

Ref1


Pic courtesy of Stan Swan.

They look to provide about an 11.4 dbi gain in a straight line and around 9 dbi around 25 degrees off axis.

Also, D-Link actually sells upgraded antennas for their routers. They seem to just use a standard BNC connector for the antennas, or at least mine does.

Incidentally, if one were to use a parabolic antenna like that, how could you go about getting the signal to spread vertically more? Basically, my router is in one corner of my home on the highest level. Some computers are on the same or a slightly lower level at the other end of the apartment, then I’m also wanting to put one in the room directly below where the router would be in the bedroom. Only solution I can really see would be to put another access point/router at the other end of the apartment. Aim the one in the general vicinity of it’s receiving antenna, then aim it’s sending antenna towards the downstairs computer.

Have an empty can lying around – put it to good use:

John

Can

Pic courtesy of Gregory Rehm.

Did you ever consider building a waveguide directional antenna? Theres a pretty good howto at HERE. and they apparently perform better than most other antennas.

The there’s always the Pringle’s cantenna:

David

Your article is very timely for me. I wish to share a link/article for you and all the friends @ Overclockers.com that I think would be of interest.
The article can be found HERE.. The article gives all the materials needed and instructions on how to build a 12db wifi antenna out of a Pringles can for 6 bucks and about 45 minutes of labor time

And would you believe the “wok” antenna:

Wok

Pic courtesy of Stan Swan.

Harry

I thought you might want to look at this…
it’s an uber cheap mod that looks so getto. If you try it, and it works…let me know.
This is the link HERE.

And a bit more refined version:

Tyler

For my Wireless Technology course, one of our projects was to build a
“cantenna” (waveguide antenna using a can, usually a pringles can). Our
group decided to go all out, and we got some Galvanized piping, capped
one end, and built it within a few millimeters tolerance of the 2.4GHz
wave specifications.

It turned out very nice, if I don’t say so myself, but we ran into
issues while testing it (the card we made it for was malfunctioning, and
the new card’s pigtail we had was wired very poorly), so we never did
get a good gage of the distance.

Unfortunately, this doesn’t really add anything to your article without
real field test numbers, but I have plenty of photos of the process, and
the final version of the can. If you are interested, I can look into
building a pigtail and testing it.

Here are photos of the finished antenna HERE.

Finally, a very interesting design:

Diggrr

Here’s a link you might be interested in, for a home built antenna (not a cantenna), that’s quite simple. It’s designed by an antenna engineer
HERE.

I’ve not been able to build one as yet, I can’t seem to get my buddy (the one with a 3Meg cable connection) to put up an antenna mast yet. We’d planned on using defunct Primestar dishes as reflectors for them, but they’re supposed to work quite superbly on their own over some distance directionally.

There’s also a parabolic reflector that you can make to slip onto your existing router antenna. Made from cardboard and tinfoil (what’s simpler, or more ghetto?). I’ll see if I can dig up a link for you to that one as well.

User Experiences CONTINUED page 5…

User Experiences

Readers wrote in about their experiences – for example:

Jonathan

I too have that Netgear wireless router. I have found that elevating
it improves signal performance. In other words, do you have an attic or
bonus room (preferably cooled) or a second story? Having the Netgear
router on the second floor improved the signal strength considerably for me
(from 40% strength/20% quality to 60% strength/40% quality according to
the Netgear wireless configuration utility – which also claims its full
11 Mb thruput is possible.)

Ironically with actual overhead (from the
transmit/receive of the signal, encryption, the pass thru to the cable
modem,etc.) the 4 Mb you are getting sounds about right for this level of
technology. I doubt anyone can really achieve 10 Mb or more with the
limitations of wifi “b.”

As with real estate, it’s location, location, location:

Mike

Here’s a few tips that can help with reception:

Location can be very important. Your transmitter should be placed as high as
possible (top floor, near the ceiling) to get the most coverage in your
house/apartment. If you are only using wireless in one room, the directional
antenna is great, but if you want to move around, height can help. The fewer
walls and floors you have to broadcast through, obviously, the better.

Interference can be a big issue. Many wireless routers broadcast on the
2.4GHz frequency which is getting quite crowded these days. Wireless home
phones, headphones and speakers often use this frequency and can cause
problems. Keep them off when using your laptop, at least keep the other
transmitters away from your networking equipment. Or use phones, etc. that
use a different frequency. Many transmitters (networking, phones, etc.) can
change the channel they operate on — so experiment with that to get the
best reception. TVs and microwaves can leak on this frequency so best to
have them off, or at least out of your broadcast path.

Justin

I have had similar problems with wifi range, in my case in receiving a signal from my neighbor (150 ft. apart). I have looked around at different antennas and have found that the prices are higher for the antennas than what I spent on the router itself. So, I found some interesting websites (HERE and
HERE) on “cantennas” – the most promising being an antenna made from a coffee can.

People have achieved something like 16dbi gain at 600 ft. And, what is nice about this alternative is that the only thing you need to purchase is the connector for the router and a mount for the can. The one downside is the legal parameters of this as the antenna would undoubtedly violate several FCC regulations. I haven’t tried this method yet, but I would be interested in seeing other people’s success.

Dan

One reason you only had
mild gains by getting a better antenna was that even though the
source(router) was strong, your laptop still has a weak signal on
transmit. I bet if you tested the actual linespeed, the laptop could
receive quite a bit faster than it could send.

Also, the orientation of
laptop 802.11xxx card’s antennas is very bad, either on a PCM/CIA card
or wired near the transformer for your displays backlite. So either the
screen is distorting the signal with EMP fluctuations or the
motherboard/CPU/RAM etc is distorting the signal.

To improve to connection speed on the laptop side, I suggest getting a
USB wireless card and clipping or hanging it above your display or to
the wall where your laptop is, not blocking the signal between the
antenna and the access point.

I have a very large house and had problems getting a good signal from my
office to my garage on the opposite side of the house.

My remedy was to
actually scrap the access point and use a USB 802.11g adapter run in
Access Point Mode, and hung the thing on the wall with a homebrew
parabolic dish antenna made from small wok (check slashdot for a recent
example of this).

I did the same thing in the garage and I get an 80%
signal constantly with a connect of 54mb/s. I can consistently transfer
about 5 MegaBytes/second. I do get a 2 or 3 percent signal drop if
someone walks between the antennas but it never lowers my connect speed.

When in doubt, an exchange??

John “Hoot” Hill

I just read your article about your trials and tribulations with your wireless
router. This past winter I had a similar situation. I bought a NetGear 802.11b
wireless router and PCMCIA card for my laptop at home. It installed easily,
with the router down in the basement of my 3-story house. Coverage was abysmal,
much like what you were experiencing.

Being highly involved in RF engineering,
I was inclined to experiment with antennas, but a coworker, who had the same
make and model, also an RF Engineer, told me my coverage sounded atypical of
what he had experienced across several makes and models of wireless routers.

Since I only had the router for a day, I returned it to where I bought it and
exchanged it. It was like night and day compared to the first one. Full-scale
signal strength on all floors of my house and a walk around my property line
showed good coverage anywhere I went on my half-acre lot.

I guess the “Quality
Control” at NetGear is like most other PC peripheral companies have become. Non- existent.

Interference? You’d be surprised from where:

Cheffy

I have found that there is an interesting connection between running an
overclocked CPU (certainly, Bartons + KT6 delta do this well) and killing
the signal strength for anyone close to the PC.

2.4 GHz core = constant signal drop, and 1.5 Mb connection speed at best. 2.3 =
full power, 2.5 = full power.

As it happens, my PC is in the room above the router, and when
running at 2.4 gig, as soon as I started a game (CPU load), the cry across
the house was “Why is the internet dead?”

It took a while to realize what it was, but changing either up or down fixed
it. So, perchance, is there a 2.4 gig AMD/P4 between you and the router, or
even, does your laptop run at this frequency? if so, this might also be a
big player.

Rob

I found that in my house I couldn’t use my laptop downstairs in the living room with WEP enabled, only without and even then with disconnections (Netgear DG834G router and WG511 PC card).

It turned out that my DECT telephones were blocking the signal most of the time, and changing the channel has me happily going through three solid stone walls and even off into my back garden ,some 30 meters through the entire house without losing too much speed now. (down to 24 Mbps from 54 Mbps)

Now if I could only get WPA to work 🙂

And sometimes, it’s a puzzle:

Polarhound

I had problems with my wireless signal with less than 20′ from router to
computer.

D-Link DI614+ router (802.11B, dual antenna)
SMC 2602W PCI card (802.11B, 2db antenna)

The two ends are on different floors, almost directly vertical in
orientation. No matter what channel I used, occasionally my signal
would drop from 95%+ to 20% for lengths of time, which is enough to kill
all data transfer. Rotating the antennas did not help in the slightest.

In the end, I bought a 4db omnidirectional antenna from SMC HERE.

This antenna was on sale for $19.99 at CompUSA. I have it laying on its
side on top of my case, which points the “horizontal” coverage up in the
air, directly at the router. Since installing this antenna, my signal
strength no longer drops below 95% – this has been the best $20 I could
possibly have spent to fix the problem.

SMC makes a 6db directional version as well HERE.

Or maybe a rift in space?

Chris

I have setup about 10 wireless networks so far all but 2 work flawlessly all over the homes they are in. In the other two, there is one room in each house that will not get a signal; in fact, in one of the rooms I can’t even get a signal in that room if I move the router and the laptop into that room and place them next to each other. If you ever run across anything to fix this type of black hole I would appreciate hearing about it.


And finally, why not overclock your wifi:

Mats

From the picture at the end of your article, I noticed that your AP is one that can be modified by putting in modified firmware. One of the features of Sveasoft’s firmware is that you can boost the output power significantly. Thus some obstacles of bad reception are remedied. I’ve put the relevant url at the bottom.

On a side note, If you raise the output to high levels, you ought to install active cooling in it.

Sveasoft’s firmware.

Thanks to all who responded – far too many to include all emails; rest assured if you’ve had some signal problems with your wireless setup, you’re not alone! And the fix may be in your cupboard.

Email Joe

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