The Dipole Antenna Isn’t As Simple As It Appears

August 16, 2023 by 47 Comments

Dipole antennas are easy, right? Just follow the formula, cut two pieces of wire, attach your feedline, and you’re on the air.  But then again, maybe not. You’re always advised to cut the legs a little long so you can trim to the right length, but why? Shouldn’t the math just be right? And what difference does wire choice make on the antenna’s characteristics? The simple dipole isn’t really that simple at all.

If you’ve got antenna questions, check out [FesZ]’s new video on resonant dipoles, which is a deep dive into some of the mysteries of the humble dipole. In true [FesZ] fashion, he starts with simulations of various dipole configurations ranging from the ideal case — a lossless conductor in free space with as close to zero diameter conductors as the MMANA antenna simulator can support — and gradually build up to more practical designs. Continue reading “The Dipole Antenna Isn’t As Simple As It Appears” →

Ask Hackaday: Why Retrocomputing?

August 16, 2023 by 81 Comments

I recently dropped in on one of the Vintage Computer Festival events, and it made me think about why people — including myself — are fascinated with old computer technology. In my case, I lived through a lot of it, and many of the people milling around at VCF did too, so it could just be nostalgia. But there were also young people there.

Out of curiosity, I asked people about the appeal of the old computers on display there. Overwhelmingly, the answer was: you can understand the whole system readily. Imagine how long it would take you to learn all the hardware and software details of your current desktop computer CPU. Then add your GPU, the mass storage controllers, and your network interface. I don’t mean knowing the part numbers, specs, and other trivialities. I mean being able to program, repair, and even enhance it.

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Giving Solar Power’s Mortal Enemies A Dusting Without Wasting Water

August 16, 2023 by 28 Comments

A prerequisite for photovoltaic (PV) and concentrated solar power (CSP) technologies to work efficiently is as direct an exposure to the electromagnetic radiation from the sun as possible. Since dust and similar particulates are excellent at blocking the parts of the EM spectrum that determine their efficiency, keeping the panels and mirrors free from the build-up of dust, lichen, bird droppings and other perks of planetary life is a daily task for solar farm operators. Generally cleaning the panels and mirrors involves having trucks drive around with a large water tank to pressure wash the dirt off, but the use of so much water is problematic in many regions.

Keeping PV panels clean is also a consideration on other planets than Earth. So far multiple Mars rovers and landers have found their demise at the hands of Martian dust after a layer covered their PV panels, and Moon dust (lunar regolith) is little better. Despite repeated suggestions by the peanut gallery to install wipers, blowers or similar dust removal techniques, keeping particulates from sticking to a surface is not as easy an engineering challenge as it may seem, even before considering details such as the scaling issues between a singular robot on Mars versus millions of panels and mirrors on Earth.

There has been research into the use of the electrostatic effect to repel dust, but is there a method that can keep both solar-powered robots on Mars and solar farms on Earth clean and sparkling, rather than soiled and dark?

Continue reading “Giving Solar Power’s Mortal Enemies A Dusting Without Wasting Water” →

Dielectric Mirror Shines Bright

August 15, 2023 by 31 Comments

We knew the mirrors in our house were not really very good mirrors, optically speaking. Your mirror eats up 20 to 40 percent of the light that hits it. High-quality first-surface mirrors are better, but [Action Lab] has a video (see below) of something really different: a polymer dielectric mirror with 99.5% reflectivity. In addition, it has no Brewster angle — light that hits it from any angle will reflect.

Turns out something that thin and reflective can be hard to find. It also makes a little flashlight if you roll a tube of the material and pinch the back end together. The light that would have exited the rear of the tube now bounces around until it exits from the front, making it noticeably bright. The film comes from 3M, and apparently, they were surprised about the optical properties, too.

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2023 Cyberdeck Challenge: A Ham Radio Cyberdeck

August 15, 2023 by 27 Comments

Cyberdecks rock because their homebrewed nature lets them feature all kinds of nifty additional functionality. [Kaushlesh] has built his deck with an eye to ham radio use, and it’s a rugged and impressive thing.

The deck is built into a weatherproof enclosure, with various 3D-printed parts helping to integrate the components into the clamshell enclosure. It runs on a Raspberry Pi 4, with [Kaushlesh] springing for the hefty model with 8GB of RAM. It has a 10-inch LCD screen and a rechargable battery pack with an impressive 20 hour battery life, and is intended for use when [Kaushlesh] is out camping or participating in ham radio field days. To that end, it’s equipped with a USB software-defined radio module and a BNC connector for hooking up an external antenna. It also has a game controller that mounts inside, just in case he desires playing a few games on Retropie while he’s out and about. It’s even got storage for a mouse and rocks a decent-sized keyboard inside.

We’d love to tote this to a hamfest for a bit of hacking on the side. It’s not the first ham-themed cyberdeck we’ve seen, either. Now we just need one built for prosciutto. Video after the break.

Continue reading “2023 Cyberdeck Challenge: A Ham Radio Cyberdeck” →

Mobile phone reading an NFC tag with information on a garden plant

NFC Puts A Stake In The Ground

August 15, 2023 by 21 Comments

Sometimes we have a new part or piece of tech that we want to use, and it feels like a solution looking for a problem. Upon first encountering NFC Tags, [nalanj] was looking for an application and thought they might make a great update to old-fashioned plant markers in a garden. Those are usually small and, being outside 24/7, the elements tend to wear away at what little information they hold.

traditional plant marker

[nalanj] used a freeform data structuring service called Cardinal to set up text information fields for each plant and even photos. Once a template has been created, every entry gets a unique URL that’s perfect for writing to an NFC tag. See the blog post on Cardinal’s site for the whole process, the thought behind the physical design of the NFC tag holder, and a great application of a pause in the 3D print to encapsulate the tags.

NFC tags are super hackable, though, so you don’t have to limit yourself to lookups in a plant database. Heck, you could throw away your door keys.

Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The QWERTY Drum Set

August 15, 2023 by 1 Comment

What does portability in a keyboard mean to you? For Hackaday’s own [Brian McEvoy], the image evokes that quintessential 80s instrument, the keytar.

But those left-hand keys aren’t just for show — they’re macro keys. It runs on an Adafruit Feather 32u4 Bluefruit, so [Brian] can forego the cord and rock out all over the room.

I love the construction of this keyboard, which you can plainly see from the side. It’s made up of extruded aluminum bars and 2 mm plywood, which is stacked up in layers and separated with little wooden donuts acting as spacers. Unfortunately, [Brian] accidentally made wiring much harder by putting the key switches and the microcontroller on different planes.

Although you could theoretically use any key switches for this build, [Brian] chose my personal and polarizing favorite, browns. If you’re going to use a travel keyboard, you’re probably going to be around people, so blues are probably not the best choice. With browns, you kind of have yourself a middle ground, best-of-both-worlds thing going on. The keycaps are among the best parts of this build, and it seems [Brian] chose them because the legends are on the sides, which makes it much easier to type on while wearing it. Kismet!

Continue reading “Keebin’ With Kristina: The One With The QWERTY Drum Set” →