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Blog moved
Moving to https://kpreid.dreamwidth.org/
(In the event that you are looking at this post in a distant future where both are abandoned, check my web site for the freshest link.) -
Representing the radio spectrum as spatial audio
Background
In software-defined radio, there are well-established ways of visually representing the signal(s) in the entire bandwidth available from the hardware; we create a plot where the horizontal axis is frequency (using the Fourier transform to obtain the data). Then either the vertical axis is amplitude (creating an ordinary graph, sometimes ( Read more... ) -
The actual base of decibels
The usual definition of the decibel is of course that the dB value y is related to the proportion x by
y = 10 · log10(x).
It bothers me a bit that there's two operations in there. After all, if we expect that y can be manipulated as a logarithm is, shouldn't there be simply some log base we can use, since changing log base is also a ( Read more... ) -
What I've been working on: ShinySDR
As vaguely promised before, another update on what I've been working on for the past couple of years:
ShinySDR (why yes, I am terrible at naming things) is a software-defined radio receiver application.
Specifically, it is in the same space as Gqrx, SDR#, HDSDR, etc.: a program which runs on your computer (as opposed to embedded in a standalone ( Read more... ) -
A Visual Introduction to DSP for SDR - now live in your browser!
My interactive presentation on digital signal processing ( previous post with video) is now available on the web, at visual-dsp.switchb.org! More details, source code, etc. at the site.
(P.S. I'll also be at the next meetup, which is tomorrow, January 21, but I don’t have another talk planned. (Why yes, I did procrastinate getting this site set up ( Read more... ) -
A Visual Introduction to DSP for SDR (video)
I have really failed to get around to blogging what I've been doing lately, which is all software-defined radio. Let's start fixing that, in reverse order.
Yesterday, I went to a Bay Area SDR meetup, “Cyberspectrum” organized by Balint Seeber and gave a presentation of visual representations of digital signals and DSP operations. It was very well ( Read more... ) -
Game idea: “Be Consistent”
Here’s another idea for a video game.
The theme of the game is “be consistent”. It's a minimalist-styled 2D platformer. The core mechanic is that whatever you do the first time, the game makes it so that that was the right action. Examples of how this could work:
At the start, you're standing at the center of a 2×2 checkerboard of background ( Read more... )
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Help me name a game keybinding library.
(I could say some meta-commentary about how I haven't been blogging much and I've made a resolution to get back to it and it'll be good for me and so on, but I think I've done that too many times already, so let's get right to the actual thing...)
( Read more... ) -
How to really fix a bug
If you're feeling virtuous:
- Figure out what's going on.
- Figure out why what's going on wasn't immediately obvious.
- Make it so that such failures are caught and reported obviously.
- Make it so that the rest of the system recovers from such failures.
- Write a test for the bug, and a couple more while you're at it.
- Write the actual fix.
(I ought to do ( Read more... ) -
Language design idea: pure name-spaces
One of the nice things about Common Lisp is the pervasive use of (its notion of) symbol objects for names. For those unfamiliar, I'll give a quick introduction to the relevant parts of their semantics before going on to my actual proposal for a “good parts version”.
A CL symbol is an object (value, if you prefer). A symbol has a name (which is a ( Read more... )