brainwagon

Yesterday’s video showed a very fussy version of Tetsuo Kogawa’s 1 transistor FM transmitter, which worked after a fashion, but which seemed really squirrely. Almost any motion of anything caused the circuit to behave rather badly as capacitance changed, and I picked up a considerable amount of hum. Today, I rebuilt the circuit onto a […]

I’ve received two requests for information about my “video production pipeline”, such as it is. As you can tell by my videos, I am shooting with pretty ugly hardware, in a pretty ugly way, with minimal (read “no”) editing. But I did figure out a pretty nice way to add some watermarks and overlays to […]

A couple of days ago, I mentioned Tetsuo Kogawa’s MicroFM transmitter, a simple one transistor FM radio transmitter. Tonight, I decided to put it together on an experimenter’s breadboard. I didn’t have the 2SC2001 transistor that Tetsuo Kogawa used, so I just dusted off one of my $.10 2N3904 transistors, and dug the rest of […]

I’ve been interested in LOWFER radio (low frequency radio operation) for quite some time. Under Part 15, unlicensed experimenters can transmit signals in the frequency band between 160khz and 190khz, subject to certain regulations on power and antennas. You can read more about it here. I was bored the other day, so I decided to […]

In thinking about the 555 timer AM transmitter that I constructed last night and trying to understand how it might work, I eventually ended up with a basic question about PWM modulation. It boiled down to this: if you are generating a pulse width modulation signal with a rate of (say 540khz) but pulses whose […]

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 […]

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 […]

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 […]

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 […]

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 […]

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.

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 […]

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 […]

Here’s an interesting project: a tube based regenerative receiver that uses an LM386 as an audio amplifier. Wacky. Still, it appears to only use 12v supplies, which may make it a fun and interesting project. The “Speaky” HF SSB transceiver and other homebrew projects: Tube/Valve receiver… the schematic Addendum: Apparently this YouTube video served as […]

Okay, I’ve been thinking (somewhat abstractly, since I have had relatively little free time lately) about what I eventually want my beacon transmitter to be. One of the issues with it is that I’d like it to be relatively autonomous and lower power: I’d like it to be able to run for weeks at a […]