The need for clear and reliable communication has driven technology forward for centuries. The longer communication’s reach, the smaller the world becomes. When it comes to cell phones, seamless network coverage and low power draw are the ideals that continually spawn R&D and the eventual deployment of new equipment.
Almost all of us carry a cell phone these days. It takes a lot of infrastructure to support them, whether or not we use them as phones. The most recognizable part of that infrastructure is the communications tower. But what do you know about them?
Continue reading “A Field Guide to the North American Communications Tower”
Back in 2007, [Stathack] rented an apartment in Thailand. This particular apartment didn’t include any Internet access. It turned out that getting a good connection would cost upwards of $100 per month, and also required a Thai identification card. Not wanting to be locked into a 12-month contract, [Stathack] decided to build himself a directional WiFi antenna to get free WiFi from a shop down the street.
The three main components of this build are a USB WiFi dongle, a baby bottle, and a parabolic Asian mesh wire spoon. The spoon is used as a reflector. The parabolic shape means that it will reflect radio signals to a specific focal point. The goal is to get the USB dongle as close to the focal point as possible. [Stathack] did a little bit of math and used a Cartesian equation to figure out the optimal location.
Once the location was determined, [Stathack] cut a hole in the mesh just big enough for the nipple of the small baby bottle. The USB dongle is housed inside of the bottle for weatherproofing. A hole is cut in the nipple for a USB cable. Everything is held together with electrical tape as needed.
[Stathack] leaves this antenna on his balcony aiming down the street. He was glad to find that he is easily able to pick up the WiFi signal from the shop down the street. He was also surprised to see that he can pick up signals from a high-rise building over 1km away. Not bad for an antenna made from a spoon and a baby bottle; plus it looks less threatening than some of the cantenna builds we’ve seen.
For a university project [Adam Libert] decided to make his very own parabolic hot dog cooker. Now, we must say, this is a project that could probably be cobbled together in a weekend from scraps, but since it was for a lab, [Adam] decided to go all out — complete with a perfect laser cut frame.
The objective of the lab was to design a project that can use solar radiation to accomplish a task, and being partial to hot dogs, the hot dog cooker was a natural choice. He designed the parabolic mirror to focus 1/5th of a square meter of sunlight directly at a hot dog. To do this, he laser cut the frame out of MDF, and using tinfoil, toothpicks, and poster paper, assembled the mirror. The whole thing cost less than $5 (ignoring laser time) and can be setup in a matter of minutes.
He determined the heat output of the cooker to be around 10W at the hot dog, which means he was able to bring the hot dog to 150°F in about 10 minutes — which was surprisingly close to his original calculations, because let’s face it, tin foil is hardly an ideal mirror.
Interested in other solar cookers? Why not cover a satellite dish in foil tape? Or if you want a quicker-cooked-hot-dog, why not plug it directly into the wall?
Parabolic microphones are used to listen in from a distance. You see them on the sidelines of NFL football games, but they’re part of the standard issue in detective and spy novels. Now you can build your own parabolic microphone by following this example.
The one component that may be hard to find is the parabolic reflector. You cannot simply use a bowl or other curved object as the precise parabolic shape ensures that sound waves are reflected onto one finite focal point. For this build the reflector was obtained from an eBay seller. But the other parts are scavenged from easy to find sources. The microphone itself is an inexpensive element from Radioshack. It is mounted in the shell from a tweeter speaker, which helps to gather the sound if the element isn’t exactly aligned with the focal point. The setup also needs a preamplification system, which uses many components. Luckily there’s a schematic and other reference material linked in the write up.
You can also build a laser microphone which detects sound waves on a pane of glass.
The wooden frame seen above hosts a parabolic reflector making up one side of a wireless network link. This is a Fab Lab project called FabFi which uses common networking hardware to setup long-distance wireless Ethernet connections. It’s a bit hard to tell in the image above, but the reflector focuses radio waves on the antennae of a router we’re quite familiar with, the Linksys WRT54G. It’s held upside-down in an enclosure meant to protect it from the elements. The node above manages to complete a connection spanning 2.41 miles!
One of the core values of the project is to develop hardware that is easy to build with limited resources, then to make that knowledge freely available. Anyone who has the ability to download and print out the 2D design file can build a reflector for themselves. As we’ve seen in other projects, paper stencils and hand tools can handle this job with no need for a laser-cutter (which was used for the prototype). WRT54G routers are inexpensive and the project uses the open source firmware OpenWRT. They can be run from 12VDC power which means a car battery works when mains power is not an option. The system has been running in Afghanistan for two years and hardware failure is still in the low single-digits.
Here is a classic project used to increase wireless signal strength. Cantennas focus using a waveguide very much like a magnifying glass focuses light. [Robert] made a Natural Light beer cantenna, pictured in the upper left. His approach used three beer cans, a paper towel holder, and a shower curtain rod. On the tipline, he noted a signal boost from 11Mbps to 54Mbps. This is certainly something we can hack together if our room lacks adequate signal. Read about parabolic and seeking versions after the break.
Continue reading “Various Cantenna builds”