#tree wifi

[kindaspookymedia]

Buttons that @jess-kitten @ferret-roulette and @chiropterax worked on to sell at conventions! We're working on even more designs, so keep an eye out! Also, if there are any designs you'd like to see please let us know!

[dragon-on-a-scooter]

New Goal

Create a tree that gives off wifi.

[tree-wifi]

That moment we got our OpenWRT router connected to the Internet.

[tree-wifi]

South America, especially Peru for some reason, has a big free WIFI movement. Lots of interesting, cheap and efficient designs are shared on forums. Just google “construir antena omnidireccional ranurada” for this particular tall slot design.

The top image is from ‘Red Libre Paraguay’ (Free Net, Paraguay)

[tree-wifi]

amazing blog about designing WIFI antennae

[tree-wifi]

Since early 2004, the TIER group has been studying how to use wireless networks to bring affordable Internet access to rural communities, especially in developing nations.  Our groundbreaking research and development has led to countless field deployments serving deserving communities the world over.  These deployments have been performed not only by us and our many partners, but also by activists who have downloaded our free code and used it globally.

JaldiMAC: WiFi has been promoted as an affordable technology that can provide broadband Internet connectivity to poor and sparsely populated regions.  A growing number of deployments, some of substantial scale, are making use of WiFi to extend connectivity into rural areas. However, the vast majority of the 3.5 billion people living in rural villages are still unserved. To reach these people, new technology must be developed to make small rural wireless Internet service providers (WISPs) profitable.

We have identified radio towers as the largest expense for WISPs; to reduce or eliminate this barrier to entry, we propose a novel point-to-multipoint deployment topology that takes advantage of “natural towers” such as hills and mountains to provide connectivity even over great distances. We make this design practical with a new TDMA MAC protocol called JaldiMAC that (i) enables and is optimized for point-to-multipoint deployments, (ii) adapts to the asymmetry of Internet traffic, and (iii) provides loose quality of service guarantees for latency sensitive traffic without compromising fairness.  To our knowledge, JaldiMAC is the first integrated solution that combines all of these elements.  

[tree-wifi]

This paper describes how shrubs have been used as transmitting and receiving RF antennas. The variations of transmitting and receiving characteristics with moist and dry conditions have been studied extensively. It has been found out that the two sets of observations differ by 5-7dB. Modulated wave transmissions and receptions have been studied as well. The behaviour of such antennas are found similar to capacitive loaded T dipole antennas as the Antenna Factor in both the cases are comparable by around 10 dB. Finally it is found that mobile phone receptions are possible with a good performance.

Published in:

India Conference (INDICON), 2010 Annual IEEE

Date of Conference:17-19 Dec. 2010

[tree-wifi]

Multi-band tree antenna patent filed 2008

FIG. 4 illustrates an operational concept of the current probes 14. In the receive mode, an external electric field induces current (I) on the tree 12. The current (I) may be coupled from the tree 12 via the current probe 14 transfer impedance to the input of a receiver or multi-coupler. The current probe 14 may be designed such that the current probe 14 will produce a desired transfer impedance Zt over the frequency range of interest and provide the required out-of-band rejection from a co-located transmit system to protect the receive system from damage or electromagnetic interference (EMI) problems. In this instance, the transfer impedance Zt=Vout/Iin. For transmitting, the primary winding 20 may generate high magnetic fields (H) in the ferrite core 16. This magnetic field (H), which equals I/2πr, where “r” is the radial distance from the center of the tree 12 to the field point, induces current (I) on the tree 12, which then radiates the energy.

Initial placement location of each current probe 14 on the tree 12 may be determined by using the length of a ¼-wavelength monopole antenna over a certain band from the following equation: ¼-wavelength=λ/4=c/4f λ=wavelength (m) c=speed of light (300×106 m/s) f=frequency (Hz) For example, the current probes 14 may be initially arranged on the tree 12 utilizing the total height of the tree 12 with the lowest-frequency current probe 14 positioned near the base of the tree 12. Then, each current probe 14 may be “tuned” by moving the current probe 14 up and down the tree 12 or its various branches until the approximately lowest VSWR is achieved. This process then repeats for the next-higher-frequency current probe 14. After each current probe 14 has been initially placed, the VSWR corresponding to each current probe 14 may be measured again. To compensate for minor impedance coupling interaction between the tree branches and the current probes 14, the positions of all the current probes 14 may be adjusted again, following the above procedure, until satisfactory VSWR performance is achieved for each current probe 14.

FIG. 5 shows a perspective view of one embodiment of the multi-band tree antenna 10. In FIG. 5, the multi-band treeantenna 10 comprises a first current probe 14 1 designed to transmit and receive in the HF range (2-30 MHz), a second current probe 14 2 designed to operate in the VHF range (30-300 MHz), a third current probe 14 3 designed to operate in the UHF range (300-1000 MHz), and a fourth current probe 14 4 designed to operate in the L-band range (1000-2000 MHz). As shown in FIG. 5, the first current probe 14 1 may be coupled to a HF transceiver 36. The second current probe14 2 may be coupled to a VHF transceiver 38. The third current probe 14 3 may be coupled to a UHF transceiver 40. The fourth current probe 14 4 may be coupled to a L-band transceiver 42. In this fashion, the tree 12 behaves as the antenna element and the ground 44 that the tree grows out of functions as the antenna ground.