Instructables

Long Range Off the Grid WiFi Repeater

Hello Everyone, 

I've got quite the project that I am undertaking and I am looking for a bit of advice. This will be my very 1st forray into long-distance wifi, as well as off-grid power resources, so Im biting off quite a bit at once! I have a friend who has been helping me with the research who has a much firmer understanding of both electricity and hardware, but he will be out of town for the next week and I would like to get a bit of progress on this while he is gone. SO, I shall consult the hive mind known as the internet.

Alright, this project consists of creating an uplink between a remote shed, and a home in a nearby city, with a broadband connection. The rub, there is 10,000 ft mountain range in between the two. We have a site were we can put a repeater node at approx. 10,000 ft elevation, that has wonderful line-of-sight to both locations. However, this site is very remote, and will have to run off the grid obviously.

The distances are as follows:

Home to repeater: 3.96 miles (thats with Google Earth following the contours of the          mountain/valley, not sure how to make it just do a straight angled shot, so thats a rough estimate)
Repeater to Remote shed: 2.68 miles (same issue)


Background environment info: shed has generator + 60w solar array with 3-4 deep discharge lead RV batteries at 7400 feet. Has spring fed running water, which could be utilized for power as well, as obviously its always running.

Repeater location is at 10k, as stated. Moderate to high winds very likely (data from peaks of similar altitude in the general area show gusts ranging from 40-60 mp/h, temperature ranges of  averaging 7 to 90+ for a the later part of July and August (F). Obviously, its very possible to get soemething below this, though the lowest Ive ever seen at the shed has been -15 (f), I would say most winters we could get a few nights that see temps below 0, but not often.


Equipment Ideas:

So to pull this off, we have come up with two ideas for the network equipment, which I shall discuss 1st, then I will show you what we have come up with for power.

 - Network
   - Repeater Node: rb433 wireless access point ($99.00)
http://www.routerboard.com/pricelist.php?showProduct=43
        with 2 r52h mini PCI wifi chips ($59.00 x2)
http://www.routerboard.com/pricelist.php?showProduct=69

        2 8-18 inch satelite dishs converted for long-range WIFI use (20.00 x2)
http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/

OR instead of a rb433, we could use 2 WRT54G Linksys routers like this. (I also have 2 BEF 801.11b routers that are legacy to the WRT54G. I would like to use this if possible!
http://hackaday.com/2005/08/23/how-to-greyhat-wifi-repeater/

Now, I know that this later choice would increase power use by about double. From what I have been able to find, the WRT's would at anywhere from 4.2w to 8w of power. Anyways, I like this later choice because it would be significantly cheaper for the equipment, but do you have any other ideas? I know that the RB433 would work great, but its rather expensive all said and done after I throw up the power as well. Plus, if it takes a lighting strike, its out of commission, and 2 cheap linksys routers are much cheaper to replace! Anyways any input here would be great!

- Power
 so power to the repeater node is the real challenge. We crunched the numbers and came up with something almost exactly the same as below:

From the datasheets, a routerboard will draw between 6-10W. So design for 10W. Over 24 hours you will need 10Wx24h = 240 Watt.Hours of power.
For 7 days, you need 7x240Wh = 1680 Watt.Hours. A single, large deep cycle 110Ah 12V battery gives you about 1320 Watt.Hours of power, almost meeting the requirement.
Now, to look at the solar panels:
A good rule of thumb is to install 6 times the wattage that is drawn by the device. This is because only about 8 hours a day in sunny weather gives you maximum power output from a solar panel. So the other 16 hours you need to draw from the battery. (So already you need 3 times the wattage drawn by the device to break even each day) To generate 1 full day of extra battery power per sunny day, you need another 3 times the wattage. This is how we arrive at 6 times.
6 x 10W = 60W. So at a minimum I would recommend 60W of solar panels.


That qoute comes from http://diywifilink.wordpress.com/ and http://mybroadband.co.za/vb/showthread.php?179547-Advice-needed-Setting-up-wifi-repeater-11km which is a project from a guy in South Africa almost exactly the same as the one that we are working on. The numbers came out to be about the same (Though they were a bit different when we calculated for the WRT54G option.)

so, 60w of power generation to keep a decent charge on a battery. Now, we have a 60w panel at the shed, which is rather large to take up to 10,000 ft and place on the side of a mountain, and given the consistent wind element up there, we are hoping to do a hybrid system of both solar and wind. This is where things get tricky. A perfect balance, or even a more wind heavy balance would be great, such as 30-40w wind 20-30w solar. That keeps the panel size down, and uses a power source that runs 24/7.

A Faroun Savonius wind turbine seems like the best system, but the controller to prevent overcharging etc is where I get nice and lost, having breached into very unknown territory. http://www.instructables.com/id/Faroun-Savonius-Wind-Turbine/

http://www.fieldlines.com/board/index.php/topic,129060.html This looked at 1st like a good, cheap system to use a controller board for the wind, but my question is would the controller board that comes with these solar panels (see below) work for both. That below is the setup that we use more or less at the shed, with some mods, such as a better alternator.

http://www.costco.com/Browse/Product.aspx?Prodid=11298029&search=solar&Mo=5&cm_re=1_en-_-Top_Left_Nav-_-Top_search&lang=en-US&Nr=P_CatalogName:BC&Sp=S&N=4001192&whse=BC&Dx=mode+matchallpartial&Ntk=Text_Search&Dr=P_CatalogName:BC&Ne=4000000&D=solar&Ntt=solar&No=3&Ntx=mode+matchallpartial&s=1&topnav=&Nty=1&s=1

So, can a small, 30-50w wind turbine and generator be built, with a small solar array to power this thing? I dont care if we have some down time, this is primarily going to be used as a system to get a weather station with web cam to send in hourly photos during the peak hours. I can have the system at the shed shutdown automatically  using some cron jobs in linux during the evening to conserve power. When there are people at the shed, we would like to be able to get a good enough wifi connection to use a wifi device (such as an android phone or ipod) to use as a voip phone in essential communication. The teenagers aren't going to be chatting with their friends for hours, but we would like to be able to put a short call through in case something goes wrong, or we just need to get ahold of someone at the shed or in the city.

Next the equipment at the shed should be comparable to the repeater node,  sans 1 antenna and just some low power embedded system. We would like to get a webcam and weather station hooked up on this end, but that can wait for upgrades later if needed, if power doesnt allow it. like I said, a simple water turbine could be used (something similar to the wind turbine perhaps?) and even another wind turbine could be built to add extra power dedicated to running any system at the shed, though I dont think the wind is quite regular enough to be viable here, but if its cheap, we could throw it on anyways.

equipment at the home in the city is simple, just use an extra laptop or desktop we have laying around to be server/router, hook up antenna to this, broadcast connection, run the weatherstation/webcam web server off of this.

So, thats the plan, but load of input is needed to try to come up with this. We hope to try to keep this sub $1000.00, but the budget could go higher. This is DIY at its finest! Thanks in advance for you help!


ojthecat3 years ago
Ok. I would try to use a passive repeater. At those distances and with high power at each end you basically would wire two wave guide antenna's back to back with a very short high quality cable. Then you need no batteries or solar.
I'd give that a shot too. Steve
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