Everyone needs wireless, sometimes around town there are wireless hotspots left open at shops, libraries, and other places that you can connect to. Sometimes you may find yourself across the park but out of wireless, or maybe youre someone who has a large plot of land and wants to get wireless at an outbuilding, or to control a robotics project. Here is a solution that can be had with a few basic tools, an hour or two of your time, and is completely mobile.
What we are essentially doing is taking a DD-WRT router and mounting it in the middle of a satellite dish. We are not making any other special antennas or adding anything else. The reason for this? the KISS method. In a time of emergency or a pinch you probably wont have too many extra materials, or time. This is thought out using yesteryears hardware. Don’t get me wrong, if you SPENT MORE MONEY on hardware you can get much more range.
Why the WRT-54 Linksys router? for those who don’t know, they made history as the original hackable router. Findable in almost any big box store in the computer section they were even inexpensive at the time, reliable, were made of quality components.. All while maintaining a secret level of expandability available to those with the appetite for it. You can actually break out two serial ports! I’m serious, wireless router for your robot control! Anyway check your local Craigslist, they are 15-25 dollars, and I didn’t need one with a power supply so I got an even bigger discount.
The other reason the router was chosen is because its powered off of 12 volts! This means that you can source some car batteries to power your wireless network. Lets say you want to extend a network a really long distance, you may be able to setup a few of these in line, with car batteries, and even solar cells. (I am working on such a packaged project actually) My version 2.0 of the WRT-54G router had a rated current draw of 1amp, with an average sized car battery that puts out 50 – 75 amp hours, you’re looking at 2 good days, maybe 3 sometimes more of solid use. This of course can be offset with solar, although a panel with enough current output to overcome the 1amp draw and charge the battery in a full day may be not practical cost wise.
Bill of Materials:
Linksys WRT-54G Router, or other router that is compatible with the DD-WRT Firmware
Directv or other small dish
Pole or other means of mounting the dish in a portable manner
The first thing you’ll want to do is build your power cable for the router. There are a couple of different approaches one can take with this depending on whats available.
Solution A) Cut the pigtail off the included wall wart / power brick if the router came with one. Then you can go to your local radio shack or auto parts store to get the ends either for a battery like actual battery clamps, or clips like those that are on jumper cables, but a smaller version. Use a multimeter/voltmeter set on resistance or continuity, or test light to find which wire goes to the center post of the barrel style power connector, this is your positive and the outside part is negative.
Solution B) You have your own collection of barrel connectors or pigtails from that huge tangled ball of old power cords in the closet and you can just cut one of that fits to your liking. Just like above Use a multimeter/voltmeter set on resistance or continuity, or test light to find which wire goes to the center post of the barrel style power connector, this is your positive and the outside part is negative. Add on your clips from the autoparts store or radio shack and you’re done.
Solution C) This was what I did, why? Because all of the adapters I had actually were in use on something else, and my box of wallwarts were all missing ends (haha go figure.) I opened the router and actually soldered wires in place of the barrel connector, and then added my battery clips that I had on hand in a parts box. (this is why you literally save anything electrical) This is recommended for advanced users only.
Now it’s time to prep the router with our custom firmware. For this project I have chosen the DD-WRT firmware, this is probably the most tedious part of the project but thats what makes it fun right?
The DD-WRT main site is located at http://www.dd-wrt.com/site/index http://www.dd-wrt.com/wiki/index.php/Main_Page
Now when you pick up your router and look at the bottom, you’ll need to carefully look at the label to determine which revision/model of router you have, then you need to search and cross reference it with the table located here: http://www.dd-wrt.com/site/support/router-database
If you are using a WRT just type “wrt54g” (minus quotations) into the search box and it will pull up a full firmware list detailing which is for which model and revision. After clicking on the one you want you’ll be presented with a large list of different types of firmware you can download, you’ll want the “Standard Generic” version, as pictured below:
Download the file to a safe place, we have located the software for your router. Now we are ready to rock, here is the actual flash guide for the WRT54G revision 2.0 router to install DD-WRT: http://www.dd-wrt.com/wiki/index.php/Linksys_WRT54G_v2.0
Other routers hardware guides are usually here: http://www.dd-wrt.com/wiki/index.php/Hardware-specific
YOU NEED TO FOLLOW THE HARDWARE SPECIFIC GUIDE TO THE LETTER! THIS INCLUDES STUDYING THE PEACOCK ANNOUNCEMENT AT THE TOP, AND DOING ALL REQUESTED HARD RESETS!
So after your router is setup, its time for configuration. I have found that pre-configuration doesn’t really do too much. You’ll want to set your wireless AP name and such so you can connect to your access point, and get to the router configuration page. Remember that when you goto deploy, you’ll need an Ethernet cable for any hangups you encounter especially if you need to factory reset again.
The cool thing I learned once in the field is under the statistics >> wireless section there is a button for site survey, this allows you to view the networks within range, and there is even a connect button! After hitting connect you are taken to the page to select repeater bridge. Make sure your WAN settings are set to DHCP and NOT disabled.
Deployment as a Repeater:
DDWRT is very flexible software, the flexibility provided being able to set an access point as a repeater is the best, it will even extend the range of a WPA network as long as you feed it the appropriate key, you will just need to pick the network security settings you need.
The guide I initially referenced for my first attempt at setting up a repeater is located here: http://lifehacker.com/5563196/turn-your-old-router-into-a-range+boosting-wi+fi-repeater
Once all preliminary configuration is done its time to mound the Router to the dish. If weatherproofing is a worry this a good time to address that issue by either sealing the existing enclosure, or finding a new waterproof one altogether. At OccupyDenver, where this dish is deployed they put a trashbag over the top of the dish and router with negligible signal loss. You’ll want to match the antennas so they are as centered on the dish as possible, this is crucial!
I ditched the LNB bracket and nonsense because of the way it angles the antenna being pointed at the dish, which means you would almost have to point the dish at the ground to get the signal to beam straight across the park or where ever, which is why I mounted the router in this fashion. You’ll want to angle the dish so it points perfectly level with the ground, or slightly elevated depending on your target.
I marked, center punched, then drilled holes in the dish where each foot was, and put on a fresh coat of paint. Next I then used self tapping screws I had on hand to secure the router to the dish, and voila! Inexpensive, deployable network from recycled e-waste!
If you find that mounting the router in the center of a dish doesn’t get you enough signal gain, sounds like you’ll need to make an antenna to attach to the dish, since the WRT54G uses external antennas, this would be the next logical step: http://www.turnpoint.net/wireless/cantennahowto.html
In my experience in the field, I found that angling each antenna toward the center essentially pointing at each other to form a triangle was the best working solution. You wont want the antennas touching the dish or each other.
There are many ideas for improvement, this is intended to be quick and dirty by purpose for the occupy Denver protesters. In the event the police come and take there camp, there is no major loss of equipment. (disposable, well I would be very sad but you know)