WiFi Antenna for point to point @1.65 miles? - Canadian TV, Computing and Home Theatre Forums
Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #1 of 45 (permalink) Old 2009-11-16, 01:46 AM Thread Starter
 
Join Date: Oct 2009
Location: Kitchener, Ontario
Posts: 597
Question WiFi Antenna for point to point @1.65 miles?

Hopefully it's okay to ask the question here in this forum. Seems there is a lot of expertise in antennas here.

I want to connect my place - 15 floors up in an apartment to my friends house that is 1.65 miles apart - direct line of sight.

What would be the best antenna to do this, or is this even possible?

--- information that may be relevant --
I'll be using the Atheros CM9 wifi cards -
http://www.mini-box.com/s.nl/it.A/id.387/.f
http://resources.mini-box.com/online...CM9/specs.html

card has two antenna connections if needed. It can do 2.4 or 5.8 Ghz, 802.11/a/b/g

I don't know anything about antennas, I'm a computer programmer than can easily build linux kernels, drivers, etc. etc. I have two left over SBC's (Wrap 1C from PC Engines with these wifi cards) from a project I did some 4-5 years ago using nycwireless pebble to create free wifi access points. I'd like to connect my house to my friends house via wifi.

----

Thanks for any help, if you have any other questions, feel free to ask.
hkaye is offline  
Sponsored Links
Advertisement
 
post #2 of 45 (permalink) Old 2009-11-16, 10:44 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Im not sure how those cards connect up, but for an antenna, a bi-quad on an old small satellite dish will give you about 24 - 31 dbi, which should be plenty and is simple to build. Im very happy with my non dish biquad.

http://martybugs.net/wireless/biquad/
http://koti.mbnet.fi/zakifani/biquad/
http://www.trevormarshall.com/biquad.htm

Analysis of the biquad here : http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/

For feeding a dish, you want to stick to the basic biquad, not the double biquad.
The biggest losses you face with wifi is the antenna coax cable, which can be horrific. The cable must be kept very short, about a couple of meters max.
Quote:
2 x UFL Ultra-miniature coaxial connectors
This sounds very bad. Skinny coax has the highest losses.

Another option is to scrap those wifi cards and put a USB wifi adapter at the focal point of a dish. Then you can use slightly longer USB cabling.

WiFi distance record: 237 miles : http://www.engadget.com/2007/06/19/v...ord-237-miles/

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #3 of 45 (permalink) Old 2009-11-16, 11:37 AM Thread Starter
 
Join Date: Oct 2009
Location: Kitchener, Ontario
Posts: 597
hmmm, no sense in using these boards if I have signal loss from the connector.

Here is a pic of single board computer with two wifi cards.



Each card has two ultra miniature connectors. The main antenna connector is in the corner if you are using is the one coax connection. I have mini cables that are about 11.5 inches long that break out the ultra miniature connector to an N-connector. If there is significant loss using this method then I'll have to look into a different wifi card - like the USB you mention that doesn't have these type of connectors.

Also, if I decide to go 802.11a at 5.8Ghz does the antenna scale linearly (can I change the dimensions to a fraction of 2.4/5.8 the lengths) or does the physical properties of the antenna change because of the higher frequency and at this point some sort of wave guide is better.
hkaye is offline  
 
post #4 of 45 (permalink) Old 2009-11-16, 11:58 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Yeah, with those skinny cables, I wouldnt be surprised youre losing 2 dbi between the board and the connector pictured above. Is there a number on that cable ? Then we could look up the specs.

Quote:
Also, if I decide to go 802.11a at 5.8Ghz does the antenna scale linearly (can I change the dimensions to a fraction of 2.4/5.8 the lengths) or does the physical properties of the antenna change because of the higher frequency and at this point some sort of wave guide is better.
The biquad does seem to scale nicely, but it would have to be modeled to make sure. Also, at 2.4 Ghz its a small antenna to start with. At 5.8 Ghz it would be about half as small, so harder to build and adjust in some ways. Plus the analysis shows its sensitive to wire size. At 5.8 Ghz, that would be very skinny wire and make it very delicate.

Quote:
like the USB you mention that doesn't have these type of connectors.
Also, USB ones arent that pricey. Ive seen them at newegg recently for $10 - $12 on sale with free shipping. 7 ft of wifi cable with connector is that much,(and thats dirt cheap for it, heh.) 15 ft usb 2.0 extention cable is cheaper.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #5 of 45 (permalink) Old 2009-11-16, 12:28 PM Thread Starter
 
Join Date: Oct 2009
Location: Kitchener, Ontario
Posts: 597
Unfortunately no markings or numbers on the cables. I would assume if the cable isn't even marked it can't be that great in quality. I'm going to source a better wifi radio.

However, those plans look great for turning these single board computers into simple wireless access points for shorter distances. I can use the sheet metal the board is attached to as a reflector. If I can get better wifi coverage in my apartment that would be great too.
hkaye is offline  
post #6 of 45 (permalink) Old 2009-11-16, 01:07 PM
Veteran
 
Join Date: May 2009
Location: Mississauga
Posts: 7,895
Quote:
I wouldnt be surprised youre losing 2 dbi
"dBi" refers to antenna gain relative to a theoretical single point antenna. When you're discussing gain & loss in amplifiers, cables, etc. you just use "dB", which expresses a ratio of output/input. Please note it is an upper case "B".
JamesK is online now  
post #7 of 45 (permalink) Old 2009-11-16, 01:29 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Yeah, force of habit to type dBi, heh.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #8 of 45 (permalink) Old 2009-11-16, 01:34 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
However, those plans look great for turning these single board computers into simple wireless access points for shorter distances.
Yep. My little biquad with the 123mm reflector, 29mm lips, gets me solid, all bars connection. My garage computer, 200 ft away, downloads/uploads exactly as fast as my indoor computer which is connected to the router via cat 6 ethernet cable. Test download/upload speeds here : http://speedtest.net/
I can also pick up the neighbors wifi at over 400 ft with the signal going thru a foil wrapped house.

Cant ask for any better, heh. (and 10X better than the (freebie with router) 6dBi Dlink antenna that I sent back )

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #9 of 45 (permalink) Old 2009-11-16, 09:21 PM
 
Join Date: Sep 2006
Posts: 123
suggesting 24dBi parabolic dish

You can get 24dBi parabolic dish antenna for 2.4GHz for a very cheap price, relatively speaking (of the gain). They look like a BBQ grill except it is curve in a parabolic shape, and has a dipole antenna sticking out. About $60. each, but sometimes you get bulk discount.

You should keep the thin cable, because you cannot attach thick cable to the card without damaging things. Just use as short as possible on the thin cable, and then connect to thick cable, low loss ones (like Times Microwave LMR-400), depending how long a run you need. The cable could cost more than the antenna, if it is a long run, plus the connector. Keep that in mind.

The advantage for a parabolic dish antenna is not only the gain, but the rejection of other signals from other locations not in the direct gain path (straight ahead) is much better than other antenna types. If the dish is too bulky for your installation, then try to use a multi-element yagi design, which is also directional.

The problem with WiFi is not just about the path loss, but there are many other signals on the same channel(s), causing interference, as there are only 11 channels used in North America, and those channels also overlapping each other (mutually exclusive only 1, 6, 11). So you want to have the least interference as possible, and a dish is the better method.

I bought mine from L-Com (actually Hyperlink which got bought out by L-Com) but there are many makers.
fortissimo is offline  
post #10 of 45 (permalink) Old 2009-11-16, 11:59 PM Thread Starter
 
Join Date: Oct 2009
Location: Kitchener, Ontario
Posts: 597
That's why I'm considering going 802.11a which is at 5Ghz, to get around the 2.4GHz clutter.

Looks like I can get minipci wifi radios with MMCX connectors, the pigtails seem to be rated at 0.7db loss. Don't know if this is good or better.

Is there a legal limit to transmit power? I can get higher power radios rated between 500mw to 1000mw.

hmm... there is a measurement for transmit in dBm. One card that looks good is rated 26 dBm for 24Mbps.

Well, this is going to be a learning experience figuring out the right radio. Seems a parabolic antenna is the way to go for a tight beam between the two locations.
hkaye is offline  
post #11 of 45 (permalink) Old 2009-11-17, 03:22 AM
 
Join Date: Dec 2006
Posts: 531
Had 2.4 wireless Internet service for a few years here and the curved dish(barbecue look referenced above) We communicated across a lake at more than 4 miles and it was great service. I would use those antennas. The regular coax from the antenna to the PC was over 50 feet.
dennism3 is offline  
post #12 of 45 (permalink) Old 2009-11-17, 07:25 AM
Veteran
 
Join Date: May 2009
Location: Mississauga
Posts: 7,895
That 50' would cost you a significant amount of signal, depending on cable type. With microwave it's all about path gain/loss. Modern industrial microwave links place the radio right at the dish and run ethernet down to the network.
JamesK is online now  
post #13 of 45 (permalink) Old 2009-11-17, 12:25 PM
 
Join Date: Nov 2004
Location: Windermere, BC
Posts: 1,312
Sounds like you're technically inclined enough to design your own equipment, but for those of us who aren't, I've solved my range problems with these products: http://www.engeniustech.com/datacom/...ory.aspx?id=17 from EnGenius. I use an outside omni-directional WAP to send the signal around our resort. It covers 2.5 Ha nicely, but they also make directional transmitters and receivers for your application.

Sony KDL-52XBR4,SD DVR530/630,Tosh HD-A2 HD-A30, Pana DMP-BD65, Pio VSX-1015,Energy C3,CC100,ESM-4,S8.2, Engenius WAP
BCScott is offline  
post #14 of 45 (permalink) Old 2009-11-17, 12:46 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
You can get 24dBi parabolic dish antenna for 2.4GHz for a very cheap price, relatively speaking (of the gain). They look like a BBQ grill except it is curve in a parabolic shape, and has a dipole antenna sticking out. About $60. each, but sometimes you get bulk discount.
Old Dish Network or PrimeStar etc dishes found along side the road or at flea markets are way cheaper, heh. LMR-400 is pricey stuff.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #15 of 45 (permalink) Old 2009-11-18, 11:34 AM
Veteran
 
Join Date: Nov 2003
Location: Kincardine ON.
Posts: 4,451
Better than a USB-WiFi adapter is an Ethernet-Wi-Fi bridge. You can run ethernet as long as you need, and make a POE adapter to send power to the unit on the Ethernet cable. You can get such units made for outdoor use.
classicsat is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome