Something To Think About While You’re Mowing The Lawn

Well here we are, we’ve reached that time of year again at which our yearly ritual of resuscitating small internal combustion engines from their winter-induced morbidity is well under way. It’s lawn mowing season again, and a lot of us are spending our Saturday afternoons going up and down our little patches of grass courtesy of messers Briggs and Stratton. Where this is being written, the trusty Honda mower’s deck has unexpectedly failed, so an agricultural field topper is performing stand-in duty for a while, and leaving us with more of the rough shag pile of a steeplechaser’s course than the smooth velvet of a cricket ground. Tea on the lawn will be a mite springier this year.

When you think about it, there’s something ever so slightly odd about going to such effort over a patch of grass. Why do we do it? Because we like it? Because everyone else has one? Or simply because it’s less effort to fill the space with grass than it is to put something else there? It’s as if our little pockets of grassland have become one of those facets of our consumer culture that we never really think about, we just do. Continue reading “Something To Think About While You’re Mowing The Lawn”

Mechanical Image Acquisition With A Nipkow Disc

If you mis-spent your teenage years fishing broken televisions from dumpsters and either robbing them for parts or fixing them for the ability to watch The A Team upstairs rather than in the living room as I did, then it’s possible that you too will have developed a keen interest in analogue television technology. You’ll know your front porch from your blanking interval and your colour burst, you might say.

An illustration of a simple Nipkow disk. Hzeller (CC BY-SA 3.0).

There was one piece of television technology that evaded a 1980s dumpster-diver, no 625-line PAL set from the 1970s was ever going to come close to the fascination of the earliest TV sets. Because instead of a CRT and its associated electronics, they featured a spinning disk with a spiral pattern of holes. These mechanical TV systems were quickly superseded in the 1930s by all-electronic systems, so of the very few sets manufactured only a fraction have survived the intervening decades.

The spinning disk in a mechanical TV is referred to as a Nipkow disk, after its inventor, [Paul Gottlieb Nipkow]. [Nipkow] conceived and patented the idea of a spinning disk with a spiral of holes to dissect an image sequentially into a series of lines in the 1880s, but without the benefit of the electronic amplification that would come a few decades later was unable to produce a viable system to demonstrate it. It would be in the 1920s before [John Logie Baird] would develop the first working television system using [Nipkow]’s invention.

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The PDP-1: The Machine that Started Hacker Culture

One of my bucket list destinations is the Computer History Museum in Mountain View, California — I know, I aim high. I’d be chagrined to realize that my life has spanned a fair fraction of the Information Age, but I think I’d get a kick out of seeing the old machines, some of which I’ve actually laid hands on. But the machines I’d most like to see are the ones that predate me, and the ones that contributed to the birth of the hacker culture in which I and a lot of Hackaday regulars came of age.

If you were to trace hacker culture back to its beginning, chances are pretty good that the machine you’d find at the root of it all is the Digital Equipment Corporation’s PDP-1. That’s a tall claim for a machine that was introduced in 1959 and only sold 53 units, compared to contemporary offerings from IBM that sold tens of thousands of units. And it’s true that the leading edge of the explosion of digital computing in the late 50s and early 60s was mainly occupied by “big iron” machines, and that mainframes did a lot to establish the foundations for all the advances that were to come.

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The Red Special: Brian May’s Handmade Guitar

Guitarists are a special breed, and many of them have a close connection with the instruments they play. It might be a specific brand of guitar, or a certain setup required to achieve the sound they’re looking for. No one has a closer bond with an instrument than Brian May to his Red Special. The guitar he toured with and played through his career with Queen and beyond had very humble beginnings. It was built from scratch by Brian and his father Harold May.

A young Brian May playing the brand new Red Special. Note the disk magnets of the original handmade pickups

It was the early 1960’s and a young teenaged Brian May wanted an electric guitar. The problem was that the relatively new instruments were still quite expensive — into the hundreds of dollars. Well beyond the means of the modest family’s budget. All was not lost though. Brian’s father Harold was an electrical engineer and a hacker of sorts. He built the family’s radio, TV, and even furniture around the house. Harold proposed the two build a new electric guitar from scratch as a father-son project. This was the beginning of a two-year odyssey that resulted in the creation of one of the world’s most famous musical instruments.

Brian was already an accomplished guitarist, learning first on his dad’s George Formby Banjo-ukulele, and graduating to an Egmond acoustic guitar. Brian’s first forays into electric guitars came from experimenting with that Egmond. If you look close, you can even see the influence it had on the final design of the Red Special.

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On Point: The Yagi Antenna

If you happened to look up during a drive down a suburban street in the US anytime during the 60s or 70s, you’ll no doubt have noticed a forest of TV antennas. When over-the-air TV was the only option, people went to great lengths to haul in signals, with antennas of sometimes massive proportions flying over rooftops.

Outdoor antennas all but disappeared over the last third of the 20th century as cable providers became dominant, cast to the curb as unsightly relics of a sad and bygone era of limited choices and poor reception. But now cheapskates cable-cutters like yours truly are starting to regrow that once-thick forest, this time lofting antennas to receive digital programming over the air. Many of the new antennas make outrageous claims about performance or tout that they’re designed specifically for HDTV. It’s all marketing nonsense, of course, because then as now, almost every TV antenna is just some form of the classic Yagi design. The physics of this antenna are fascinating, as is the story of how the antenna was invented.

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History of Git

Git is one of those tools that is so simple to use, that you often don’t learn a lot of nuance to it. You wind up cloning a repository from the Internet and that’s about it. If you make changes, maybe you track them and if you are really polite you might create a pull request to give back to the project. But there’s a lot more you can do. For example, did you know that Git can track collaborative Word documents? Or manage your startup files across multiple Linux boxes?

Git belongs to a family of software products that do revision (or version) control. The idea is that you can develop software (for example) and keep track of each revision. Good systems have provisions for allowing multiple people to work on a project at one time. There is also usually some way to split a project into different parts. For example, you might split off to develop a version of the product for a different market or to try an experimental feature without breaking the normal development. In some cases, you’ll eventually bring that split back into the main line.

Although in the next installment, I’ll give you some odd uses for Git you might find useful, this post is mostly the story of how Git came to be. Open source development is known for flame wars and there’s at least a few in this tale. And in true hacker fashion, the hero of the story decides he doesn’t like the tools he’s using so… well, what would you do?

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How a Hacker Remembers a PIN

If you have more than a few bank cards, door-entry keycodes, or other small numeric passwords to remember, it eventually gets to be a hassle. The worst, for me, is a bank card for a business account that I use once in a blue moon. I probably used it eight times in five years, and then they gave me a new card with a new PIN. Sigh.

Quick, What’s My PIN?

How would a normal person cope with a proliferation of PINs? They’d write down the numbers on a piece of paper and keep it in their wallet. We all know how that ends, right? A lost wallet and multiple empty bank accounts. How would a hacker handle it? Write each number down on the card itself, but encrypted, naturally, with the only unbreakable encryption scheme there is out there: the one-time pad (OTP).

The OTP is an odd duck among encryption methods. They’re meant to be decrypted in your head, but as long as the secret key remains safe, they’re rock solid. If you’ve ever tried to code up the s-boxes and all that adding, shifting, and mixing that goes on with a normal encryption method, OTPs are refreshingly simple. The tradeoff is a “long” key, but an OTP is absolutely perfect for encrypting your PINs.

The first part of this article appears to be the friendly “life-hack” pablum that you’ll get elsewhere, but don’t despair, it’s also a back-door introduction to the OTP. The second half dives into the one-time pad with some deep crypto intuition, some friendly math, and hopefully a convincing argument that writing down your encrypted PINs is the right thing to do. Along the way, I list the three things you can do wrong when implementing an OTP. (And none of them will shock you!) But in the end, my PIN encryption solution will break one of the three, and remain nonetheless sound. Curious yet? Read on.

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