High Gain Wifi Antennas, Im Confused

[FXGuy3369]

I have a store, and we are opening another store across the street, approx 1/8 mile away. There is a somewhat big building in between. I am shopping high gain antenna's but do not know what is necessarily more important, the MW rating or, what dbm antenna I use, should it be omni directional, or not because I know where the source is I want to pick up. Here are a few I was looking at. Any input would be greatly appreciated.

http://cgi.ebay.com/NextG-USB-Yagi-...ltDomain_0&hash=item5d283425f5#ht_8152wt_1140

http://cgi.ebay.com/Marine-RV-38dBm...ltDomain_0&hash=item20b265ff10#ht_10506wt_952

http://cgi.ebay.com/50dBm-USB-WIFI-...tDomain_0&hash=item53e2d8e82e#ht_10318wt_1008

 

[theevilsharpie]

If you've got a building obstructing your view, you're not going to get a reliable connection no matter what antenna you use.

 

[Jimmah]

Can you get any sort of line of sight? If so, you 'might' get away with a directional, but it may/will be as evilsharpie says and be rather unreliable.

Other option would be optical wireless like the DIY RONJA, there are non-homemade options available but they are expensive.

 

[FXGuy3369]

I know the building is going to be an issue, I was wondering if somebody could explain how much of a difference higher Mw ratings will make?

 

[spidey07]

You only have so much energy, that's what the radio puts out. An antenna does nothing more than focus this energy. So higher gain = more narrow/precise beam.

There is nothing you can do if there is a building in the way except go higher than the building for line of site.

 

[JackMDS]

What realty count is the dbm.

If you have a 1000mW antenna and you "pump" into it 2000mW than you need a 2000 mW Antenna, otherwise you might damage the Antenna or the output Amp. of the Access point.

2.4GHz can not be "pump" through Building and 1/8 mile regardless of the Antenna used.

 

[Modelworks]

You need the antenna higher than the building or you need a path around the building. If you can maybe find someone in the area who would be willing to let you set up a relay point that would be the best way to handle it. Then you would send from store #1 to the the relay then to store #2.

Higher on one end of the signal is another option. You would need a tower to clear the obstruction + fresnel zone. Add about 10ft clearance to whatever blocks the path.

To get a signal through a structure for something like wifi you would be in the illegal and unsafe to humans power range.

 

[WildHorse]

Just ask the property manager for the obstructing building for permission to put your gear atop his roof. Maybe put one WiFi repeater on each of the two edges of his roof facing each of your two locations.

Doubt they'd care. Why would anyone object?

Maybe offer to sign some sort of waiver of all liability in case your guy gets hurt on his property.

 

[bobdole369]

mw rating indicates "how much power" the antenna can take before derating and/or melting elements.

No way you are shooting through a building 1/8 mile. I had clear LOS and all manner of device available, 24dbi dish, 14dbi yagi, 8dbi patch, 6dbi vertical. In the end the 6dbi vertical worked best. The high gain ones turn into a laser and vibrations cause multipath distortion.

I had a serious problem with the fresnel effect at my distance. I had a bunch of vegitation growing up into it and that was likely a big factor in the unreliability of that link. Also ahuge lake reflecting things all over the place off to the right (or left).

A building - forget about it. Pony up the cost of business and get a ptp or a a half a t-1 in each loc. even dsl with a couple ptp vpn devices would do.

 

[Emulex]

with mimo you might be able to pull it off with 3 transmitting antennas? try it.
the buffalo 2.4ghz runs 20hz (150mbps max) channel 6 at 830mw which you can up to 1 watt (naughty). then you can pop the two main antennas off and cantenna them. If you get smart you can do the third which is just reverse socketed and run 3 antennas. at 14dbi gain you would have hella power (more than legal). also with a ham license the atheros chipset can go from 2.4 - 2.6ghz (2.5-2.6 is wimax ). they also make a higher band 5ghz that goes up to 6.1ghz. you would have more legal luck if you were a technical or expert ham license you could then use some other bands.

the best way i've seen is using lower bandwidth. like VHF/UHF you can go much farther but at a lower symbol rate. I guess 1megabit at 95% reliability is better than 11megabit at 15% reliability huh?

when my buffalo WZR is doing 40-wide at 630mw pretty much everything else in the house dies when i'm pushing 16MB/s down or up (16 megabytes 160megabits). can't get it to go faster without another channel (60-wide) sadly.

trendnet makes some cool stuff that uses 750 (3xmimo) and quantenna and 1 other source used a proprietary 4x mimo for 1000megabit.

the laws are pretty cool to ham radio licensees. alot more bands to pick from and higher power output. you should really check it out !

i remember 30 years ago i got technician class to do modem over mountains (packet radio) back in the 80's it was hard as heck you had to learn morse code but now i think they dropped it to a prometric class that is easy as all heck

 

[bobdole369]

From a hobbyist point of view this is great. One caveat - no way you can get away with trying to part 97 a businesses wifi link. I'm pretty sure its only about half the 802.11b/g band too - just the upper 6 channels that exist in the amateurs arsenal.

General class here.

 

[piasabird]

My friend uses wifi directional antenna mounted high on a HAM radio tower. He is outside of town in a more isolated area surrounded by trees, with no other form of internet access. He has a amature radio license.

 

[ScottMac]

My friend uses wifi directional antenna mounted high on a HAM radio tower. He is outside of town in a more isolated area surrounded by trees, with no other form of internet access. He has a amature radio license.

A ham license doesn't cover all bands, just the Amateur Radio bands. It's still a violation. It's still up to $10K fine for a first offense (however unlikely).

I'm an Extra class, trust me.

 

[bobdole369]

Oh and forget about using WEP or WPA if you plan to operate under part 97 rules. Encryption of any kind is simply prohibited. Communications of an explicit nature (obscene) are also prohibited, and station ID is required every 10 minutes. He can mount the thing up there and use all the free wifi he wants, but he's operating under part 15 rules.

 

[JoLLyRoGer]

Alternatively you could try down converting into the 900MHz band and boosting up your power. 900MHz has much better near and non line of site RF propagation characteristics than 2.4GHz.

Basically the lower you go in the spectrum the better your signal will propagate and the deeper penetration it will have inside of buildings and such. Part of why 700MHz is to attractive for LTE operators.

Not sure what the FCC says is the max EIRP (that's insertion power + antenna gain FYI) for non licensed 900MHz but you can definitely find antennas to handle as much as you want. I'd suggest something like a 35 or 60 degree sector panel that would give you relatively high gain characteristics and a little bit of a footprint coverage since you don't know exactly where the other end is.

But let me also state one side of the link is only half the battle. The other end must also be able to make the reverse path home .. So whatever you do on one end you should consider doing to the other too. In that case you might as well get a pair of highly directional Yagi's, go for the gain, and do a proper antenna alignment.

So, as others have said (and we've come full circle here), outdoor antennas and clear line of sight are your best bets Even if it means putting up a truss style tower on your roof (think of the old style Log Periodic TV antennas)

Just some more food for thought.
JR

 

[drebo]

Honestly, 1/8th mile isn't very long. Unless you're shooting through the building long-ways, it shouldn't diffuse the signal that much. If you use something like 900mhz, you should have no problem at all.

Get some Ubiquiti NanoStation M900s and you'll be able to do a point-to-point bridge and get 80+ megabits out of it.