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.

Turbot is a Beam/Picaxe Hybrid

BeamBot

[James] wanted to build a BEAM turbot. He ran into some problems with the BEAM circuitry though, and ended up with a BEAM/Picaxe hybrid.
Beam robotics are the brainchild of Mark Tilden. The acronym stands for Biology, Electronics, Aesthetics, and Mechanics. BEAM based bots were very popular with hobbyists in the 90’s and early 2000’s, but popularity has since died down. BEAM robots tend not to use microcontrollers, instead attempting to simplify things down to the lowest number of elements.

[James’] turbot uses a miller solar engine. The original design used the engine to drive a Solar Turbot Latch. [James’] problem was that the photodiode “eyes” of the robot were not properly enabling the 74AC245 to pass current to the motor. Since the robot was built in a tiny space, debugging the circuit was extremely hard. After struggling with the ‘245 for some time, [James] decided to swich out the BEAM circuit for a Picaxe microcontroller.

The Picaxe can only sink or source about 20ma per pin, which is slightly less than the no load current of [James’] motors. To make up for this, he ganged up four pins per motor. There was some risk in the motors blowing up the Picaxe. However between the lightly loaded gearmotors and low current solar panels it seems to be working just fine.  Overall the bot is a very clean, compact build. Jump past the break to check out its really smooth crablike walking action.

[Read more...]

BEAM robot tumbles aimlessly

[Harm's] tumbling robot from a few years back is an excellent study in simple motion. Foregoing wheels or legs, he uses four flippers to roll the robot around the room. Two motors are used, each in charge of two flippers. Identical but separate circuits drive the motors with a 74HC240 gate IC monitoring the continuously rotation. When a flipper becomes stuck, the circuit reverses the rotation of the motor so the simple bot can tumble its way out of a jam.

The circuitry is less advanced than some of the BEAM builds we’ve seen before. That doesn’t diminish the cleverness of his design and we think BEAM robotics are great way to get your head out of the computer code and go hardware only. After the break you can take in some video of the  tumbling motion. We’ve also included a video of another bot from his website that uses concentric rings for another type of unique locomotion.

[Read more...]

Tiny projector teardown

projector

The team from Tech-On has taken the time to teardown two interesting microprojectors. The first model they tackled was the Optoma PK101. It’s based around a digital micromirror device (DMD) like those used in DLP. Separate high intensity red, green, and blue LEDs provide the light source. A fly-eye style lens reduces variations between images. They noted that both the LEDs and processors were tied directly to the chassis to dissipate heat.

The next projector was the 3M Co MPro110. It uses Liquid Crystal on Silicon (LCoS) technology. The light source is a single bright white LED. The projector seems to have more provisions for getting rid of heat than the previous one. The most interesting part was the resin polarizing beam splitter. It not only reflected specific polarizations, but also adjust the aspect ratio.

[via Make]

Spotlight on tinyminds


Etsy places a spotlight on tinyminds, creator of the much-hyped solar robots. [Jenny], the brains behind tinyminds and self-described “all round nerd and non-stop crafter”, claims to draw inspiration for her BEAM solar bug and monster robots from things as varied as paper and wood. She describes the process of creating her robots and working with solar energy as “magical”. The fact that they’re solar-powered is a huge advantage – these “pets” never die and never need recharging, only light. Her Cthulhu robot was linked to by BoingBoing Gadgets, and is unfortunately sold out at the moment. tinyminds has plenty of other inventive, equally inspiring robots available for purchase.

Solar engine


We spotted [Kerrin Mansfield]‘s lovely solar engine on ladyada’s rantings. It uses 16 1/8th inch solar cells to collect power. At night, an orange LED pulses at .2Hz. He doesn’t have a specific write up on the construction, but from the component layout, it looks identical to [Gareth Branwyn]‘s schematic in Make 08, which you can find in the PDF.

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