Pocketable Yagi Antenna Really Shoots For Distance

November 2, 2023 by Dan Maloney 45 Comments

For amateur radio operators, the quest for the perfect antenna never seems to end. Perhaps that’s because our requirements are always changing. We never quite seem to get to one design that can do everything. This copper-foil Yagi antenna might not do everything, but it really seems to tick off the boxes for gain and directionality along with ultra-portability.

If you’ve been following [Ben Eadie (VE6SFX)]’s trip down the rabbit hole of lightweight antenna building, you’ll recall that he’s already knocked off a J-pole antenna and a stealthy mobile slot antenna using little more than copper foil tape. Both of those designs performed great, but [Ben] had bigger fish to fry: he wanted to build a directional antenna for the 2-meter band and go for distance. The traditional Yagi-Uda is generally the preferred design for beam antennas, but they tend to be bulky and cumbersome. But with a roll of copper foil tape [Ben] was able to lay out a three-element Yagi on a sheet of Tyvek wrap. Reinforced with some packing tape and stiffened with a couple of fiberglass rods attached to a 3D printed handle, and it was ready to go.

[Ben]’s field test results were most impressive. Not only was he able to open up repeaters up to 90 km away, but he was getting good signal reports to boot. He was even able to reach a repeater 150 km distant, just barely though. Still, that’s mighty impressive performance from something that looks like a Union Jack and rolls up to fit in a pocket.

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Intra-Oral Device Detects Opioid Overdose

May 13, 2018 by Kristina Panos 32 Comments

As you may have heard, the U.S. is in the grips of an opioid epidemic. Overdose deaths from heroin, oxycontin, and fentanyl have quadrupled since 1999. The key to detecting opioid overdose before it’s too late is in monitoring respiration. Opioids in particular cause depressed respiration, which is slow and ineffective breathing that’s inadequate for the gas exchange that keeps us alive. Depressed respiration becomes fatal unless the patient is given nalaxone, an antidote that works by blocking opioid receptors in the brain.

[Curt White] is developing an intra-oral device to prevent opioid overdose via early detection. It tracks a patient’s inhale/exhale rate and sends the data over Bluetooth to an open-source website. The tiny device uses an air pressure sensor, a humidity sensor, and a thermopile thermometer to accurately track a person’s full respiration waveform whether their mouth is open or closed. The brain is one of [Curt]’s hacked $35 activity trackers that we told you about a few days ago.

All of the hardware including the battery is embedded in a custom retainer made from thermoplastic. [Curt] used Tyvek and surgical tape to isolate the air pressure sensor. Both are waterproof and breathable, which means that air can get to the sensor, but not saliva. Hold your breath and click past the break to watch [Curt] demonstrate this amazing tool on himself.

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Building An LED Suit

August 16, 2012 by Mike Szczys 12 Comments

[Rob] has been hard at work designing and building this LED suit which he can wear to parties. He’s got it working, although right now it’s just a pair of pants. It reacts to sound, and has the potential to be controlled from a smartphone via Bluetooth. You’ll find a video description of the build embedded after the break.

The planning started off by selecting driver hardware for the LEDs. [Rob] wanted the suit to pulse to the music in the room so he grabbed an MSGEQ7 chip. When connected to a microphone and opamp this chip will output a signal which can be used as a VU meter. He built the hardware into an Arduino shield, then got to work on the LED driver board. He’s using LED strips, but they’re not individually addressable. Instead he cut loops which wrap around the wearer’s legs. Each loop connects the pins of a TLC5947 LED driver chip which sinks a constant current and offers PWM abilities. He’s using PNP transistors on the high side.

For anyone that’s ever worked in a Tyvek suit before you’ll know they don’t breathe. Sweat will literally be pouring off of you. And we’d bet that’s what cause the short that burned the back of [Rob’s] leg at a recent party. Then again, your light-up pimp coats are going to be hot to wear too.

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