Can you use cables to extend wifi antenna?

[Grit]

I'm trying to get better wifi coverage in my home, and was considering placing the wifi antenna in the attic. This would ensure that only one "wall" (the ceiling) was in the way, which is an improvement over the 2-3 walls I have now.

Is it possible to buy/make cables to mount the antenna 6-8 feet away?

 

[Mushkins]

It's absolutely possible.

The catch is what kind of wireless router/AP you're attaching that antenna to. Check out this article for the basic concept, the section titled "Connect your Antenna to a wireless card or Access Point." It's the same idea, except you're presumably attaching it to a third-party premade antenna instead of one made out of an old can of beans.

http://www.turnpoint.net/wireless/cantennahowto.html

Linksys seems to have shunned the old school screw on antenna model for internal antennas with their latest models, but I know the higher end ASUS routers have traditional screw-on externals you could easily replace the way you're talking about. Many access points also use external antenna.

You also might want to consider that if you're dropping cable either way, just getting a second AP and spreading them out will probably be cheaper and easier than extending the antenna, as well as giving you better coverage.

 

[azazel1024]

Just check amazon or ebay. You can come across a lot of coax for wireless antennas. Just need to find what kind of antennas you need the wire for. Generally RP-SMA, occasionally it is SMA (just google RP-SMA vs SMA for pictures if your router doesn't specific).

You'll also need to ensure whatever adapter you have and router have removable antennas.

Do NOT put a USB wifi adapter in the attic and run a USB cable down to your computer. Attics frequently hit 20-40F over ambient, which means in the summer time it is likely to fry the adapter.

My question though is this, if you are planning in going to the effort to punch the wires in to the attic to begin with, why not just run cat5e from your computer to the router and do the connection wired? Little extra effort or cost. Much higher speeds.

As for wiring, keep it as short as you can. Even on quality coax, you lose signal fast over the wire, ESPECIALLY 5GHz. A 3m wire you can loose 5-6dBm on 5GHz easily and 2-3dBm for 2.4GHz. A very good wire might be half that, but you still are going to see signal loss. That is less than you'll see in loss through a typical wall, but if you are thinking of using a 10m extension to run the antennas along the attic to be over the router or something, you'll see a huge signal path loss. Like 15-20dBm at least, if not double (depending on the wire quality and it'll still have to punch through the insulation and ceiling drywall).

 

[RadiclDreamer]

Yes you can, but remember, each bit of cable has some attenuation to it and the longer you run it, the less power that is left to send out to clients, same goes with the return, if you have a client that is able to get a marginal signal to the antenna, the cable could be enough to lose more signal to the point of lowering speeds and or killing the connection.

 

[Grit]

Thanks for the input. I should have elaborated on the details:

My cable, cable modem, and gigabit switch are in a low voltage electrical box (designed for cable, phone, and network connections). I wired the house for gigabit ethernet and all the connections come back to that box. It does get warmer in there, but I have a fan on it and it's survived a few summers without incident. Next time, I'd probably put it indoors in a closet (California... no basements).

I used to have an Asus black diamond router as non-wifi in the garage, and just ran one Cat.6 into the attic where another Asus black diamond served as a wifi access point. I expected to change it yearly due to heat, but it survived 2 summers. It still runs, but I now have wifi devices that are faster than 66Mbps N, so I upgraded the router. I didn't want to risk a new router in the attic. I figure i got REALLY lucky the first time.

The original plan was to have an antenna only in the attic, but the original plan would have had a 30' antenna cable, and that's when someone explained cable attenuation to me. Thus, I gave up at the time.

Now that I moved ito one router and put it in the closet, its still a good 7' off the ground, but still has a few walls to go through. I made the mistake of not checking signal strength before I pulled it out of the attic, so I have no basis of comparison. Since I already ran electrical and Cat.6 into the closet, I figured I could just change the plate on the low voltage side (where the Cat.6 is) and run an antenna cable up about 6-8' into the attic. Then I would have line of sight with only ceiling to go through before the signal reached any given room in the house.

I'm trying to figure out if putting the antenna up there will be helpful, or if it's even necessary. According to inSSIDer, my signal strength currently ranges from -33 at best to -50 at worst (with different locations). The attenuation tables for wifi routers on SmallNetBuilder.com made me concerned, since my signal strength seems to be at the lower end, especially for 5GHz.

Signal goes as follows :
- starting in the garage, cable -> cable modem -> cat.6 through attic to interior closet -> Netgear N7000 -> cat.6 though attic to garage -> Netgear GS108 switch

From there I have several Cat.6 cables back through the attic into the house. One goes to my PC, one goes to my wife's desk (though she now uses wifi), one goes to my server (also in the garage), one goes to my workbench for when I'm working on computers, and one goes to my entertainment center, where it hits another switch and then goes to my TiVo, Oppo Bluray, and Sonos.

 

[Cabletek]

I'm trying to get better wifi coverage in my home, and was considering placing the wifi antenna in the attic. This would ensure that only one "wall" (the ceiling) was in the way, which is an improvement over the 2-3 walls I have now.

Is it possible to buy/make cables to mount the antenna 6-8 feet away?

You can not only buy antennas with cables you can buy powered antenna with a signal booster internal to them.

It depends on your router, but generally the high frequency waves of wireless services passes through standard dry wall fairly easily its denser and conductive materials like concrete or metal siding [the chicken wire used in laven plaster, etc..] they have trouble with.

 

[dealguru]

Yes, but I believe there are cables made for that purpose. Make you are purchasing the right one.

 

[JackMDS]

Coax cable running 2.5GHz attenuates the signal even with short runs.

As a result what ver is gained form better positioning of the Antenna is lost on the coax.

The solution for good coverage of WIFI is a network of Access Points.

 

[azazel1024]

The other issue you'll run in to is antenna pattern. Modest gain antennas are omni directional, but only on the horizontal plane, NOT the verical plane. They have lower gain the further off the horizontal plane you go. Something like a 5dBi antenna is going to have a pattern that results in roughly half the signal gain around 30 degrees off vertical. So if you have the antenna at the attic peak so that there is minimal wall/ceilings for the signal to pass through to wireless devices, you are likely putting a lot of the devices outside of the optimal beam pattern. You could possibly tilt the anntena, so long as you don't need any gain on the "backside" of where it is located, that would help.

A 3m good coax will not have significant signal loss, but you will still have signal loss. Figure a minimum of .5dBm per 1ft length on 2.4GHz and figure double that for 5GHz. So a 10ft wire is likely to lead to around 5dBm of loss, on the low end. That is roughly equivelent to a typical double drywall wall with 2x4 construction.

If in an attic, you are also likely to have long runs through the ceiling. IE the signal is penetrating at a very oblique angle, which is worse than an accute angle where it has to penetrate less material. That plus any walls that it does have to penetrate. You also lose any bounced signal.

Within a house, at least with open doors, some of the signal is likely to bounce off walls, metal structures, etc. Sometimes the best beam path is actually from several reflections and not through direct penetration. Mounting it in the attic precludes a lot of that.

If you have the house wired for gigabit, just place the router in a fairly central location and that'll provide the best connection for the most devices. You mentioned 2-3 walls, so it doesn't sound like a big house. A decent router with decent radios and antennas should have zero problems covering something like that from a central location unless every room is a great room. If you needed to run wireless from one end of a house to another, THEN putting a couple of modest gain directional antennas in the attic pointed at each other would probably be a great idea. Just providing coverage to a house though isn't a great idea.

You are better off just sticking higher gain antennas on the router in a central location than you are trying to place them in the attic. Especially if it is an older home. A lot of the homes built in the 1950-1960s and maybe in to the early 70's as well, used FOIL backed and faced fiberglass insulation as a vapor barrier instead of a paper based vapor barrier. This, understandby, sucks for signal penetration. As an example, in my bedroom I get 3 bars on my cell phone for my wifi (IE excellent signal) with the router below me in the basement. Poping in to my attic (access is in the bedroom closet) my signal strength drops to 2 and sometimes 1 bar, only moving about 5 feet vertical...but with the foil faced and backed fiberglass insulation in the way (and about 6" of cellulose and now 10" of unfaced fiberglass on top of all that...which is why I know, as I had my cell with me as I was laying new insulation).

I did not bother to take my laptop with me to pull up InSSIDer, but at a guess, that insulation and ceiling board effectively reduced the signal strength by a good 20-25dBm...which is about the equivelent of 3 regular walls within my house.

Just regular fiberglass or cellulose insulation will attenuate signals too, though not nearly as much as the metal faced stuff does.