Archive for month: March, 2011

555 Astable Multivibrator as an AM Transmitter

March 31, 2011 | Amateur Radio, electronics, My Projects | By: Mark VandeWettering

I mostly avoided the siren song of the 555 timer that seemed to echo through the blogiverse during the recent 555 contest, but when I was out and about last weekend, I picked up 10 of them from Anchor Electronics, and they have been taunting me from the shelf ever since. So, last night I […]

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Amazing small machining site…

March 31, 2011 | Amateur Radio | By: Mark VandeWettering

Back when I was into building telescopes (something I haven’t done very much of in the last few years) I developed a desire to try some machining. I managed to pick up a 6″ Atlas mini lathe. And… well.. I’ve done very little. It’s sitting on my workbench in the garage. This website demonstrates some […]

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Neat article on William Friedman and Steganography

March 28, 2011 | Cryptography | By: Mark VandeWettering

William F. Friedman is a name that might not be familiar to you unless you are a bit of a cryptography nut. Of course, I am a bit of one: I have a couple of long technical notes that were authored by Friedman on the cracking of some complex WWI era ciphers. But I must […]

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Roger, G3XBM shows off a software VLF receiver

March 27, 2011 | Amateur Radio | By: Mark VandeWettering

Roger, G3XBM, has been busy experimenting on the Dreamer’s Band: signals somewhere around 8.9khz. These signals are actually in the audio range: so all you need to receive them are an antenna (Roger uses a largish loop antenna) and an RF preamplifier, feeding into a soundcard. Roger demos his system here, and shows reception of […]

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The HOPALONG Orbit Fractal

March 24, 2011 | Math, My Projects | By: Mark VandeWettering

While watching TV, I coded up a custom renderer for the HOPALONG orbit fractal, generated 300 frames, and encoded it with FFMPEG. Without further ado:

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HOPALONG, from Dewdney’s Armchair Universe

March 24, 2011 | Arts and Crafts, Math | By: Mark VandeWettering

All this fiddling around with the Lorenz attractor has made me try to think of other simple, easy graphics hacks that I could make. I recalled that A.K. Dewdney had some simple graphics hacks in one of his Computer Recreations column back in the 1980s. It turns out that Wallpaper for the mind was published […]

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The Chaotic Lorenz Water Wheel

March 22, 2011 | Amateur Science, Math | By: Mark VandeWettering

Doing a bit more reading, I found out that the equations that make up the Lorenz attractor (which are derived from a simplified model of 2D fluid flow with a superimposed temperature gradient) can also be thought of as governing another physical system. Imagine a water wheel, with a number of buckets spaced evenly around […]

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Chua chaotic oscillator

March 22, 2011 | Amateur Science, electronics | By: Mark VandeWettering

Over sushi this evening, Tom mentioned “Chua’s circuit”, or “Chua’s oscillator”. I knew that I had seen this somewhere before, but failed to remember that Chua was also the guy who first theorized about the memrister: a circuit element whose resistance is proportional to the sum of the charges that has been passed through it. […]

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My own animation of the Lorenz Attractor

March 22, 2011 | Amateur Radio | By: Mark VandeWettering

I’ve been working on a script or two for generating intros for some of my little YouTube videos, and thought that maybe something like an animation of the Lorenz strange attractor might make a somewhat interesting background. A little tweaking, and I produced the following example (only 10 seconds long, and with some Morse as […]

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The Strange Attraction of Strange Attractors…

March 19, 2011 | Amateur Science, electronics, Math | By: Mark VandeWettering

I’ll just lead off with a picture: This is a graph of the so-called “Lorenz attractor”, first described by mathematician Edward Lorenz in his paper Deterministic Nonperiodic Flow back in 1962. I learned about this kind of stuff probably back in highschool by reading Scientific American. Anyway, the equations themselves are pretty simple, but describe […]

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3-D printing method advances electrically small antenna design

March 16, 2011 | Amateur Radio | By: Mark VandeWettering

Antenna design and manufacture has historically been pretty, well, primitive. There are reasons for this: early on, solving the large systems of equations to adequately model complex antennas was difficult. Luckily, advances in computers and software make that much more tractable. Now, we can design antennas with dozens or even hundreds of elements, and in […]

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Followup re: crystal microphones

March 16, 2011 | Amateur Radio, electronics | By: Mark VandeWettering

A bit more digging on yesterday’s topic (crystal microphones) yielded this book, published by the U.S. Army, entitled CW and AM transmitters and receivers which included some additional useful information regarding the construction of crystal microphones.

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Cooking up piezo crystals at home

March 15, 2011 | Amateur Science | By: Mark VandeWettering

I’ve always been interested in crystals: their outer beauty hints at a certain kind of inner beauty, caused by the orderly arrangement of molecules at the atomic level. When I was a kid, I made crystals from sugar, salt, alum, and copper sulfate, but never tried Rochelle salts. Rochelle salts are interesting because they are […]

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Demo of Enigma and the Turing Bombe at Bletchley Park

March 15, 2011 | Amateur Radio, Cryptography, My Photos, My Projects | By: Mark VandeWettering

Carmen and I just got back from a trip to London, and we had a blast. One of the geekiest things we did while there was to take a day trip by train out to Bletchley Park to see the site of the codebreaking efforts by the British during WWII. As any long time reader […]

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No, really, pi is wrong

March 14, 2011 | Amateur Radio | By: Mark VandeWettering

Having completed my posting of a new program in celebration of pi day (going back to just spelling it out, since somewhere in the WordPress to Twitter chain, the HTML entities get dropped) I was reading my twitter feed, and found Vi Hart’s amusing video asserting that “Pi is Wrong”. Click through and watch the […]

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