Learning and scouting for info

•July 29, 2009 • 2 Comments

This blog will chronicle my quest to provide my parents with a telecommunications link on the farm where they live.  It is only about 10 km from town, but it is in a valley separated from town by mountains, and they have no cellphone reception and no telephone line.  I plan to put up a high site on a mountain close to them to enable them to connect to the internet via an ADSL point in town.  The high site has line of sight to town and to them.  There is also another house on the farm that is interested in getting internet access, so they will be the second client to use the link.

Any advice is welcome, so please leave a comment if you know anything about this kind of thing.  Please look at the unanswered questions at the bottom of the post and leave an answer if you have one.

All of this started as a post in the mybroadband.co.za forums.  It reads:

My parents live on a farm about 11 km outside town (as the crow flies), in a valley where there’s no line of sight to town. So they don’t even have cell phone reception. About 2 km from their house (and about 12 km from town) there’s a mountain from where you can see the town, and their house. I want to set up a wifi bridge on the mountain so they can get internet via an ADSL line in town. I’m guessing I need the following:

– Wifi router & directional antenna in town
– Router in bridge mode, with antenna that that sees both of end points (end points are separated by about 80 degrees). Solar panel & battery to give power to the bridge router
– router and directional antenna at their house on the farm

Any advice on how to do this the cheapest way?

In the mean time, we’ve found a better place for the potential high site, and the angle is now a maximum of 30 degrees(more like 23 if my measurements on Google Earth are correct).  A diagram to explain:

Map of High site and clients

Advice on the power:

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.

From the advice I got on the forum, I’ve drawn up a list of what I think I need:

Power :
– 1 x 110ah deep cycle battery – around R1000
– 50 – 60 watt solar panels – around R3000 (the sun shines most of the time, it’s in the Karoo, so think I can get away below 60 watt)
– charge regulator (around R350) (should have a battery connector, a solar panel connector and then a fused/protected 12V load output to protect your router equipment, also with auto shutdown if the battery gets too low)
– cables (around R100)
– enclosure & waterproofing (can put something together for about R100 I guess)

End points : 3 x Ubiquity NS5 (R789 each) (one for the ADSL point in town, and one each for the 2 clients)
Hisite :
– 1 x 411 / 433 Routerboard (R499 – R980)
– 1 x RB52 radio (R315)
– 1 x 2.4Ghz 14dBi 90 Degree Vertical Sector Antenna (is this the cheapest option that will work? Do I need something more expensive? Do I need something with a wider vertical beam width?) (R860)
– 1 x enclosure (R219)
– cables (around R200 I’m guessing)

Installation hints:
– Self amalgamating tape and then wrap electrical tape around the self-amalgamating tape and then cable tie the lot.
Guaranteed no water to enter that in a thunderstorm
– When you attach the uFL connector to the R52 stick some tape around that,due to temperature expansion and contraction it can pop off

Unanswered questions:

– How do I set up the high site?  As an AP or a bridge?  Ideally I want both clients to connect to their own ISP on the ADSL via PPPoE, using the wifi just as a link to extend the ADSL.

– Would I need more than one RB52 expansion card on the router board to do what I described above if there are 2 clients in the valley?

– What antenna should I use on the high site?

– How does licensing work?  Do I need a license to do this?  How much does it cost?  Is it yearly or once off? Will ICASA even know if I don’t have a license?