Category Archives: Coax

Wired Wireless Over Coax

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If it’s stupid and it works, then it’s not stupid. There’s no better evidence of that than [Tobias]’ networking setup.

He recently had to distribute Ethernet through a building, and there are a few ways to do that. You can use regular ‘ol twisted pair, or fiber, but in this case running new cables wasn’t possible. WiFi would be the next obvious choice, the distance was just a bit too far for ‘regular’ WiFi links. Ethernet over power lines was an option, but there are amateur radio operators in the house, and they put out a bunch of interference and …read more

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The BNC Connector and How It Got That Way

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When I started working in a video production house in the early 1980s, it quickly became apparent that there was a lot of snobbery in terms of equipment. These were the days when the home video market was taking off; the Format War had been fought and won by VHS, and consumer-grade VCRs were flying off the shelves and into living rooms. Most of that gear was cheap stuff, built to a price point and destined to fail sooner rather than later, like most consumer gear. In our shop, surrounded by our Ikegami cameras and Sony 3/4″ tape decks, we …read more

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What’s Special about Fifty Ohms?

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If you’ve worked with radios or other high-frequency circuits, you’ve probably noticed the prevalence of 50 ohm coax. Sure, you sometimes see 75 ohm coax, but overwhelmingly, RF circuits work at 50 ohms.

[Microwaves 101] has an interesting article about how this became the ubiquitous match. Apparently in the 1930s, radio transmitters were pushing towards higher power levels. You generally think that thicker wires have less loss. For coax cable carrying RF though, it’s a bit more complicated.

First, RF signals exhibit the skin effect–they don’t travel in the center of the conductor. Second, the dielectric material (that is, the …read more

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A Friendly Flying Robot Pet

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[luca] has always wanted a flying robot, but despite the recent popularity of quadcopters and drones [luca] has never seen a drone that is truly autonomous. Although sometimes billed as autonomous, quadcopters and fixed wing aircraft have always had someone holding a remote, had to stay in a controlled environment, or had some off-board vision system.

Computers are always getting smaller and faster, battery and motor technology is always getting better. That’s why [luca] is building a truly autonomous flying robot for the 2016 Hackaday Prize.

Since [luca] is building a coaxial copter – something that looks like a ducted …read more

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