brainwagon

Every once in a while, I feel like making high quality pictures of ground tracks of satellites. The Generic Mapping Toolkit is handy, especially when combined with the pyephem library. The thick line is the ground track of the amateur satellite AO-51, at any point in its next pass where it is visible from my […]

Some of you might be wondering what it is about this Karplus-Strong algorithm that has got me interested. Of course, long time readers of my blog might well have wondered that about any of a number of things that I’ve written about. What is it about checkers that prompted me to write a checkers program? […]

Okay, I finally found my copy of Ken Steiglitz’s A DSP Primer (a great book, but sadly more expensive now than when I got my copy) and read through the implementation of the tunable plucked string instrument. A couple of things really need to be added: first of all, I was off considerably in my […]

Well, it’s been quite some time since I tried to work any of the FM birds, but I dusted off my TH-D7A, my voice recorder and my Arrow antenna, and decided to give it a go. It was pretty busy, and as usual I found it a bit difficult to get in. I got myself […]

It appears that the solar sail cubesat NanoSail-D that was recently launched may not have deployed properly: they haven’t been able to track it or contact as of yet. Bummer. I’ve been intrigued by solar sail technology for quite some time. Here’s hoping they figure out what went wrong, but bummer thusfar. NanoSail-D Mission Status […]

The other day, I was trying to remember how to generate some simple sounds with minimal amounts of code. I remembered vaguely something called the Karplus-Strong algorithm, and it has been floating around in my head that I should look it up again. I mentioned it to Tom, and he spent 15 seconds drawing something […]

Lost in yesterday’s thrilling launch of the SpaceX Falcon-9/Dragon launch was that during their flight, they also apparently deployed a cubesat: CAERUS (which is apparently Greek for “opportunity”). It has a 900mw FM AFSK beacon downlink on 437.600, and operates under the amateur callsign KJ6FIX. I have not as yet been able to locate TLEs […]

When I was young, I used to tune into KEX 1190 in Portland during the Christmas season when they would play episodes of “The Cinnamon Bear”, a classic 1937 radio serial about Judy and Jimmy and their quest to catch the Crazy Quilt Dragon who has stolen the Silver Star on the top of their […]

Tom showed me a link to The J1 Forth CPU, a very small processor which is coded in Verilog (only 200 lines!) and can run very fast on existing FPGA boards. It is quite an intriguing design. Forth is an intriguing if somewhat archaic programming language. In the bygone ages of my youth, I experimented […]

I’ve been playing with a BASYS2 FPGA development kit from digilentinc.com, and pondering the world of digital system design. I chose the BASYS2 because of its low price ($70) and because it included a reasonable number of LEDs, switches, a VGA interface and a connector for a PS/2 keyboard. Still, I’ve been looking for other […]

Many people use computers to exchange email or pictures, to shop, or even to program for a living. I do all that kind of stuff, but one of the most pleasurable things I do with computers is to use them to answer questions or to gain insight into problems which are too difficult for pen-and-paper […]

The Wobbulator is a pretty nifty little video modification gadget. Basically, the idea is that by adding a couple of extra magnetic yokes at odd angles to the conventional yokes on a black and white display tube and driving them with a frequency synthesizer, you can create all kinds of amazing patterns. The results are […]

I’m kind of on a retro computing kick for the last few weeks. I suppose it is mostly because I picked up an FPGA board to experiment with, and I have been reading old books on computer architectures, looking for old fun machines that were simple enough to implement in VHDL/Verilog. This brought me back […]

Today, the hash function has selected The Practice of Programming by Brian Kernighan and Rob Pike. On my shelf you’ll probably find a couple dozen reference books that are written about various programming languages. This book is one of a smaller handful that literally talks about programming: how to write clear, general, reliable programs that […]

Today’s book is Mathematical Recreations by Maurice Kraitchik. As might be evident to long time readers of my blog, I have a lasting interest in what might be called “recreational mathematics”. This is a particularly challenging thing to define, since so much of what we might consider recreational mathematics unveils deep and mysterious things within […]