Wireless reception booster?

[DerStrom8]

Hey guys!

I've got a new project involving Wifi. Before now, I haven't had a computer with Wireless Internet capabilities. Now that I have one, I need a little help. I was hoping that it might be possible to build a homemade wireless "antenna" that plugs into the computer via usb, or maybe a "booster" that stands in the room that boosts the Wifi signal. I can't afford one of the actual USB wireless antennas, so I was wondering if it might be possible to make my own. I'm asking because when I get to a part of my house, I have very low signal strength. I was just hoping I could build something that can be in the room with my computer that can boost the signal strength.
Thanks a lot for any help!
Der Strom

 

[blueroomelectronics]

You might find some antenna designs on the net.

 

[Reloadron]

A Google of "Cantenna" will bring up dozens of hits including sites like this one. The trick is being able to connect it to your laptop if you are using a lap top. Most desktops with a wireless LAN card are easy to connect to. Lap tops with built in antenna produce another problem.

You can also Google for example "Pringles Can Antenna" for additional hits. Since you don't describe your WiFi configuration at home it is hard to offer much more.

Ron

 

[DerStrom8]

A Google of "Cantenna" will bring up dozens of hits including sites like this one. The trick is being able to connect it to your laptop if you are using a lap top. Most desktops with a wireless LAN card are easy to connect to. Lap tops with built in antenna produce another problem.

You can also Google for example "Pringles Can Antenna" for additional hits. Since you don't describe your WiFi configuration at home it is hard to offer much more.

Ron

The "Pringles Can Antenna" is what inspired me to give this a try, but since I do have a laptop with a built-in antenna, I don't think it will really work for me. I was thinking more along the lines of a sort of parabolic (?) reflector that would direct what signal I have straight to my computer, hopefully reducing "waste" (i.e. signal that has spread out away from my computer rather than been picked up by it). I apologize if this doesn't make much sense. I'm rather new to WiFi, and I'm just trying to learn Thanks a lot for your patience and help in this matter!
Der strom

 

[Reloadron]

This guy got creative.

I have seen a variety of schemes used at the point of the wireless router to make the router somewhat directional. The above link may be in the direction you want to go. Hey, a plastic bottle and some foil.

Ron

 

[unclejed613]

i used to make passive loop antenna boosters for AM radios. the idea being that a resonant loop antenna with a bit more "surface area" was magnetically coupled to the inefficient loop antenna in the radio. all it consisted of was a loop of wire and a capacitor to make it resonant. the loop of wire was anywhere between 2ft to 4ft diameter and the radio was placed inside of the resonant loop with the little loopstick perpendicular to the loop (the wires in both coils were parallel). a few years back there was a company that made a device for cell phones that used a similar concept. it was a piece of flexible circuit board with a loop antenna and resonating capacitance tuned for the 800Mhz cell phone band, and it stuck on the back of a cell phone, and was magnetically coupled to the short and inefficient antenna of the cell phone. you could probably do the same for 2.4Ghz by etching a piece of circuit board. a 1λ loop and a tuning capacitance could be easily fabricated on a piece of PC board. placed near the antenna of the wireless card, it might couple enough extra signal to the card to overcome the signal loss you're experiencing. a square 1/4λ on a side would be a 1λ loop. leaving a gap in one side, you could use a piece of foil tape to tune the loop (this would be the capacitor)

keep in mind that 1/4λ at 2.4Ghz is about an inch and a half...

 

[DerStrom8]

i used to make passive loop antenna boosters for AM radios. the idea being that a resonant loop antenna with a bit more "surface area" was magnetically coupled to the inefficient loop antenna in the radio. all it consisted of was a loop of wire and a capacitor to make it resonant. the loop of wire was anywhere between 2ft to 4ft diameter and the radio was placed inside of the resonant loop with the little loopstick perpendicular to the loop (the wires in both coils were parallel). a few years back there was a company that made a device for cell phones that used a similar concept. it was a piece of flexible circuit board with a loop antenna and resonating capacitance tuned for the 800Mhz cell phone band, and it stuck on the back of a cell phone, and was magnetically coupled to the short and inefficient antenna of the cell phone. you could probably do the same for 2.4Ghz by etching a piece of circuit board. a 1λ loop and a tuning capacitance could be easily fabricated on a piece of PC board. placed near the antenna of the wireless card, it might couple enough extra signal to the card to overcome the signal loss you're experiencing. a square 1/4λ on a side would be a 1λ loop. leaving a gap in one side, you could use a piece of foil tape to tune the loop (this would be the capacitor)

keep in mind that 1/4λ at 2.4Ghz is about an inch and a half...

This is exactly what I was looking for! Do you think you could attach a diagram to clarify?
Thanks a lot!
Der Strom

 

[unclejed613]

actually 1/4λ at 2.4Ghz is 1.23". the formula for λ in inches is 11.8/Ghz. then divide by 4 for 1/4λ

the following diagram is for a PC board antenna. the copper foil tape should be insulated from the copper trace. if you etch it on single sided board, you can put the tape on the opposite side of the board (don't use double sided board, the ground plane will act as a shield and the loop won't work). only use G10 fiberglass, because the phenolic cheap boards are very lossy at 2.4Ghz and won't work well. the size of the piece of foil tape is something you will have to experiment with to find the right size. for experimenting you can use aluminum foil of various sizes stuck to the blank side of the board with masking tape.

 

[DerStrom8]

actually 1/4λ at 2.4Ghz is 1.23". the formula for λ in inches is 11.8/Ghz. then divide by 4 for 1/4λ

the following diagram is for a PC board antenna. the copper foil tape should be insulated from the copper trace. if you etch it on single sided board, you can put the tape on the opposite side of the board (don't use double sided board, the ground plane will act as a shield and the loop won't work). only use G10 fiberglass, because the phenolic cheap boards are very lossy at 2.4Ghz and won't work well. the size of the piece of foil tape is something you will have to experiment with to find the right size. for experimenting you can use aluminum foil of various sizes stuck to the blank side of the board with masking tape.

Thank you very much for the info. I'll be sure to give it a try!

 

[unclejed613]

another method you could try is to build a passive repeater. make two loops, leave out the copper foil tape, and connect the two together with some coax cable (i forget the RG- number, but it's NOT RG-6, 8, 58, 59, or 174, as those types are too lossy at 2.4Ghz to be useful) the coax has to be long enough to go from the room the router is in, to the room where the computer is. there are cable losses and antenna losses that you will encounter, but it will still have more signal then if you didn't have it.



edit: not RG- type cable, but LMR-200 cable, which has a loss at 2.4Ghz of 0.554db/meter and is about the same diameter as RG-58

 

[DerStrom8]

Ok, so I dont' really have access to circuit etching equipment right now, so is there any way I could just use a piece of wire? And would it be possible to simply use a variable capacitor instead of the foil? I'm hoping I can do this with materials I already have around. Thanks a bunch!
Der Strom

 

[HiTech]

D-Link makes a high gain antenna that works well for radiating the WiFi signal from your router. My D-link dipole antenna sends my signal hundreds of feet in all directions. The weakest signal I receive in my yard is no less than 30-40%. Typical signal strength is 65% and up. Rather than drag around a directional antenna that you have to connect to your laptop, position and fiddle with, instead, increase the effective radiated signal from your router. The D-link will accomplish this for you. Also with a signal possibly extending beyond your home, you should have a WEP or WPA encryption in place.

**broken link removed**

**broken link removed**

 

[Reloadron]

Ok, so I dont' really have access to circuit etching equipment right now, so is there any way I could just use a piece of wire? And would it be possible to simply use a variable capacitor instead of the foil? I'm hoping I can do this with materials I already have around. Thanks a bunch!
Der Strom

Got an empty plastic 2 litre bottle and some foil as in aluminum foil? In my second I gave a link where I said this guy got creative. Takes a few min and as they say nothing ventured, nothing gained.

I use a set of Linksys 7 dbi antennas on my old router and I drag my laptop all over the property. But for cheap, simple and no effort try the link in my second post.

Ron

 

[DerStrom8]

Got an empty plastic 2 litre bottle and some foil as in aluminum foil? In my second I gave a link where I said this guy got creative. Takes a few min and as they say nothing ventured, nothing gained.

I use a set of Linksys 7 dbi antennas on my old router and I drag my laptop all over the property. But for cheap, simple and no effort try the link in my second post.

Thanks a lot for your responses and patience!
I was actually trying to avoid directional reflectors/antennas that attach to the router, because there are a few different places in my home with low signal. The directional reflectors make it so that some areas work, but others don't. That's why I was looking for something that could attach to or sit near my laptop, so I don't have to worry about the direction.
I still greatly appreciate your help--Perhaps I could still use a reflector sometime
Again, Thanks a lot!
Der Strom

 

[Reloadron]

Ah, now I better understand. That leaves you in the omnidirectional family with suggestions like that of HiTech which unfortunately have a cost. Relocating the router to a more central location would be a suggestion but then you need to deal with any wired devices connected to it. This brings you back to home brew omnidirectional designs. The major difference I see between the stock antennas and the 7 dbi ones I have is the overall length. Not sure what magic is stuffed in there as to wavelength but they do work well.

Ron

 

[Sceadwian]

A standard dipole is 2.5dBi. dBi means decibels compared to an isotropic antenna (a true omnidirectional antenna) there is no such thing as a true omnidirectional antenna though. the dead lower lobes of a dipole are along it's axis, the directionality is roughly toroidally shaped horizontally from the direction of the anntenna. Mind you this is relative to the wavelength involved which is quiet small so even directly above a wi-fi antenann you'll get signal for 'long' distances at least long distances on a human scale. The 7dbi antenna must be a loaded whip or dipole of some type which squashes that toroidal shape even more to give you the extra 4.5dBi. I personally think the higher quality antenna construction and the layout is probably the more determining factor.

The only other thought I have is is that 7dbi antenna plugged into the wall? IE does it have a power supply? It could be using a remote 5db discrete amplifier, the amplifier being at the antenna base in a relativly controlled environment and away from the PC itself would make an ideal preamp location.

 

[Reloadron]

The only other thought I have is is that 7dbi antenna plugged into the wall? IE does it have a power supply? It could be using a remote 5db discrete amplifier, the amplifier being at the antenna base in a relativly controlled environment and away from the PC itself would make an ideal preamp location.

Nope, there is no external power. However, since they say a picture is worth a bunch of words attached is a picture.

The original antennas are outboard with the 7 dbi inboard. They are a pair as the router uses a pair rather than a single. The router is an old Lynksys 54G series router. The antennas, like most of the junk piled up around here were given to me several years ago.

The house is an older wood frame construction with no shortage of plaster in the walls. The aluminum siding was replaced years ago with vinyl siding. So what's the difference? With the old antennas the router covered the house well, the router being located on one extreme side in the center of the house. Including the upstairs I had good usable signal. However, outside in the back yard I could not stray far. With the new antennas I can wander anywhere on my property and have really pretty good signal.

I can also sit on my neighbors (across the street) front porch and have signal, not bad. That would not happen with the OEM antennas. I set up the same neighbors WiFi but his router is in the basement (concrete pit). The same router I have and he is OK pretty much in his house but the signal isn't that great, When he uses his laptop it works well in the room directly above the router. Oh his front porch I can hardly get his router. Mine across the street has a much better stronger usable signal.

So go figure? Maybe the longer antennas are rubbed with snake oil?

Ron

 

[unclejed613]

the longer antenna is actually two antennas with a phasing coil between them. it's known as a Colinear antenna. the antenna is made up of two λ/4 radiators, and the phasing coil insures that the signal across the radiating elements are in-phase. i've seen wi-fi antennas using several colinear sections that have up to 18db of gain perpendicular to the axis tof the antenna. the signal pattern is almost pancake shaped compared to the donut shape of a dipole or a λ/4 element.

 

[Reloadron]

the longer antenna is actually two antennas with a phasing coil between them. it's known as a Colinear antenna. the antenna is made up of two λ/4 radiators, and the phasing coil insures that the signal across the radiating elements are in-phase. i've seen wi-fi antennas using several colinear sections that have up to 18db of gain perpendicular to the axis tof the antenna. the signal pattern is almost pancake shaped compared to the donut shape of a dipole or a λ/4 element.

Thank you unclejed for the informative post. This was something that seemed to work well and I never questioned the "how".

I also now am aware that there was no snake oil involved so thanks again for the clarification.

Ron

 

[Sceadwian]

Yes Jed thank you, that really clarifies things, one more antenna design I have to look up =)
So much to learn!

I am surprised that kind of antenna design isn't standard, by large and far vertical coverage isn't generally a problem.