a.ntivir.us wanted to use a different antenna for their Netgear mbr624gu WiFi router. Unfortunately, this model comes with an antenna that is not removable. As with other antenna retrofits, this involves no soldering. But because there is already a mounting area for an antenna, no case altering is needed either. After opening the router with a Torx driver it was discovered that the non-removable antenna was connected to the board with a mini rf connector (U.FL). The antenna and its mounting bracket were removed and a U.FL to RP-SMA adapter was put in its place using a washer to secure it to the rear plate of the router. Now any external antenna can be used and the router still looks brand new.
External antennas on netbooks are notorious, from EEE PCs to the Panasonic CF-R1, but this is the first on an Acer Aspire One we’ve seen. [xRazorwirex] sent in his external antenna hack for the 802.11n capable D150, with the intention of increasing performance, but he says he can’t attest to any change. Unfortunately the lock slot had to be removed, but a small price to pay for a big increase in connectivity. The process seems simple enough, and could probably be done within a half an hour. Now that there is an external link why not build a Cantenna, hop in the car, and HeatMap the neighborhood!
[Mike] takes us through the process of adding a removable high gain antenna to the WRTSL54GS in this article. The antenna that comes on this unit from the factory is a bit small and underpowered. After upgrading it using OpenWrt, an open source full featured router software package, he felt it needed a beefier antenna. So, he cracked it open. The new antenna can simply be soldered in place, where the old antenna was.
With the impending digital switchover, many of you will find yourselves not only in need of a new converter box, but an antenna as well. Just like everything else, there are plans out there on how to build your own. [William] has gone through the effort of documenting his design and build of a very nicely made version. He used PVC for the frame and a wire mesh or chicken wire reflector. Good job [William]
[Alanson Sample] and [Joshua R. Smith] have been experimenting with wireless power transfer for their sensing platform. Their microcontroller of choice is the MSP430, which we used on our e-paper clock. They chose it specifically for its ability to work with low voltages and they discus its specific behavior at different voltages. The first portion of their paper uses a UHF RFID reader to transmit to the sensor’s four stage charge pump. They added a supercap to provide enough power for 24 hours of logging while the node isn’t near a reader. For the second half of the paper, they use a UHF antenna designed for digital TV with the same circuit and pointed it at a television tower ~4.1km away. It had an open circuit voltage of 5.0V and 0.7V across an 8KOhm load, which works out to be 60uW of power. They connected this to the AAA battery terminals of the thermometer/hygrometer pictured above. It worked without issue. The thermometer’s draw on a lab power supply was 25uA at 1.5V.
It’s an interesting approach to powering devices. Do you have an application that needs something like this? For more on wireless power, checkout this earlier post on scratch building RFID tags.
[Steven] managed to get his hands on a Panasonic CF-R1 for pretty cheap. Though it is a decently powerful machine, it was built in 2002 and didn’t come with an internal wireless card. It did, however have a mini-PCI slot. [Steven] promptly installed a wireless card, but found the internal antenna lacking. The solution was to custom mount an external antenna. Mounting it was fairly easy, he removed the phone jack and epoxied the connector in its place. The reception was greatly improved. He says he went from seeing 6 access points to 31 as soon as he installed it. Similar things have been done to the Eee PC 900.
[nmarquardt] has put up an interesting instructable that covers building RFID tags. Most of them are constructed using adhesive copper tape on cardstock. The first version just has a cap and a low power LED to prove that the antenna is receiving power. The next iteration uses tilt switches so the tag is only active in certain orientations. The conclusion shows several different variations: different antenna lengths, conductive paint, light activated and more.
The device works by connecting two antennas to an enclosure that contains a speaker. The enclosure is intended to be worn on the back with a harness securing it in place and wrapping the arms around the wearer’s body. The antennas are incorporated into a pair of gloves. When the antennas pick up electromagnetic radiation, the speaker emits a low frequency sound waves. They vibrate the enclosure and the arms, which in turn vibrate the body, signaling to the wearer that he or she is in an electromagnetic field, also referred to as hertzian space. A good deal of detail about the project can be found on his blog, or if you prefer, download his thesis paper in(PDF).
We Make Money Not Art recently visited the LABoral Art and Industrial Creation Centre in Gijón, Spain. The installation that left the strongest impression on [Regine] was the WiFi sightseeing telescope built by Clara Boj and Diego Diaz. Spain is in a situation similar to the USA: A few years ago many municipal WiFi projects launched only to be squashed because of theoretical unfair competition with local utilities. Now commercial projects like WeFi, Whisher, and FON encourage people to “share” their WiFi. Observatorio (Observatory) is designed to provide insight into the current state of local WiFi. It uses a highly directional Yagi antenna to collect wireless access data from the local area. The antenna has a 30deg aperture which is matched to a camera with an identical field of view. The observer sees the camera’s viewpoint with the WiFi data overlaid showing where accesspoints are and whether the AP is open. WMMNA also recommends you check out the WiFi Camera which photographs electromagnetic space.
Monitoring medical patients remotely 24 hours a day has always proven to be a difficult proposition due the size of the wireless sensors attached to the patient’s body to relay vital signs. A team from Queen’s University Belfast has come up with a solution that utilizes the creeping wave effect. The effect applies to electromagnetic waves as they come into contact with solid objects. While the majority of the waves are absorbed by the object, a small amount move along the surface of the object before they continue their path.
Since most of the signal sent by conventional biosensors is absorbed by the patient’s body, the signal must be strong enough to compensate. The antennas designed by the Queen’s University team, though, focus their broadcast laterally instead of inward and outward, maximizing the amount of waves that will travel along patients’ bodies via the creeping wave effect and minimizing the amount that are absorbed. These antennas are up to 50 times as efficient as conventional antennas of the same size, broadcasting a stronger signal with less power.
The applications to the wireless body area networking, attaching multiple biosensors to patients’ bodies, field are obvious, but this technology could be used in other ways. Since the creeping wave antenna is small and wearable, it could conceivably be used to boost low power communication to PDAs, cellphones, or any other portable wireless product.
