Tape Measure VHF Yagi Antenna

tap measure yagi vhf antenna

Radio direction finding and fox hunting can be great fun and is a popular activity with amateur radio (ham radio) enthusiasts. These antennas are great and are not only good for finding transmitters but also will greatly increase directional distance performance including communicating with satellites and the international space station (ISS).

[jcoman] had a nephew who was interested in learning about amateur radio so [jcoman] figured building and using a cheap and portable 2 meter band VHF Yagi style beam antenna would be the perfect activity to captivate the young lad’s interest in the hobby.

His design is based on [Joe Leggio’s] (WB2HOL) design with some of his own calculated alterations. We have seen DIY Yagi antenna designs before but what makes this construction so interesting is that the elements come together using bits of cut metal tape measure sections. These tape measure sections allow the Yagi antenna, which is normally a large and cumbersome device, to be easily stowed in a vehicle or backpack. When the antenna is needed, the tape measure sections naturally unfold and function extremely well with a 7 dB directional gain and can be adjusted to get a 1:1 SWR at any desired 2 m frequency.

The other unique feature is that the antenna can be constructed for under $20 if you actually purchase the materials. The cost would be even less if you salvage an old tape measure. You might even have the PVC pipes, hose clamps and wire lying around making the construction nearly free.

We were quite surprised to find that such a popular antenna construction method using tape measure elements had not yet been featured on Hackaday. For completeness this is not the only DIY tape measure Yagi on Instructables so also check out [FN64's] 2 m band “Radio Direction Finding Antenna for VHF” and [manuka’s] 70 cm band “433 MHz tape measure UHF antenna” postings. The other Yagi antenna designs featured on Hackaday were “Building a Yagi Uda Antenna” and “Turning an Easter Egg Hunt into a Fox Hunt” but these designs were not so simple to construct nor as cleverly portable.

Weightless, the Internet of Things Chip, Becomes Less Vaporware

weightless

Several months ago, we caught wind of Weightless, a $2 chip that will run for 10 years on a AA battery and communicate to a Weightless base station 10 Km away. Yes, this is the fabled Internet of Things chip that will allow sensors of every type to communicate with servers around the world. It looks like Weightless is becoming less and less vaporware, as evidenced by the Weightless SIG hardware roadmap; Weightless modules might be in the hands of makers and designers in just a few short months.

Weightless is an extremely low-cost wireless module that operates in the radio spectrum previously occupied by analog broadcast television. This is a great place for the Internet of Things, as signals in this spectrum have a lot of range and the ability to go through walls. These signals are sent to a Weightless base station where they are then sent over the Internet to servers around the world.

The Weightless SIG has been hard at work producing new silicon, with the third generation of chips heading for volume production next month. The only thing this chip requires is a battery and an antenna, making Weightless integration for new designs and projects a snap.

There’s one thing Weightless is not, and that’s a free, high-speed connection to the Internet with a $2 adapter. Weightless is designed for sensors that only transmit a kilobyte or so a day – medical sensors, irrigation control, and other relatively boring things. There’s a summary video from the recent 2013 Weightless SIG Summit going over all this information below.

[Read more...]

UHF power harvesting

hdpowerharvesting

[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.

[via DVICE]