brainwagon

Shifting gears a little from my normal subject matter, I’ll confess to a certain literary guilty pleasure: I like the writings of H. P. Lovecraft. I’m not saying they are the highest literature: I just find them to be an interesting style, creating a mythos that I find a compelling backdrop for a collection of creepy stories. I also like things like fossils and the like (I keep an Elrathi kingii on my desk). So, I find the following craft project strangely compelling: to create Lovecraft-themed props.

Gads. Next, I’ll be making steampunk stuff…

PROPNOMICON: From the Mountains of Madness

Yesterday I managed to be the winning bidder for this little radio at the QRP Pacificon. Mike Schettler, WA6MER was kind enough to put it up, and I thank him profusely, it’s a very nice little rig. Now, I am one step closer to emulating Bill, M0HBR, as I have BOTH a Drake 2B and a Heathkit HW-8. Heh.

Addendum: My apologies for saying the word “actually” three times in once sentence. Chalk it up to me being fairly excited.

Diane, VA3DB, wanted some pictures of the Softrock Lite II kit that I built, so I fired up the Canon and snapped these.

We were fogged in here, so I didn’t have an opportunity to watch, but it looks like I didn’t miss much: early reports are that basically no one saw any visible plume, not even at Mt. Palomar. Here’s a link to Sky & Telescope’s story:

SkyandTelescope.com – News from Sky & Telescope – LCROSS Impact: It’s a Hit — But Was Anything Seen?.

The other day I was lucky enough to be invited by Bob Whitehill to share a lunch up at UCB with Marty Banks, Kurt Akeley and a bunch of other vision researchers from their lab. I was lucky enough once to have been interviewed by Kurt when he was at SGI back in 1994 or so. His office faced Moffett Field, and on that particular day, they were test flying Harriers. My recollection was that we spent time mostly discussing a program that he wrote in OpenGL to emulate the barrel distortion of fisheye lenses, and watching the Harriers go back and forth. I didn’t get the job offer, and Kurt had no recollection of it. Oh well. I suppose I remember that day pretty well because after my SGI interview, I went directly to a first date with the terrific lady who would later agree to marry me. October 25th, 1994.

Since I’ve been living in the bowels of Pixar production, I must admit that I haven’t been keeping up with Kurt’s doings, and it seems like that is a big mistake on my part. In trying to look up a paper that he co-authored with Marty et. al on stereo displays, I found his page at Microsoft which links to a lot of interesting material.

Archived for future digestion.

Kurt Akeley – Microsoft Research

This Friday the NASA LCROSS probe will deliberately impact in a dark crater on the moon, with the ultimate goal of trying to decide if any water exists on the moon in these deep craters. As it happens, I was going to take Friday off from work anyway, so being awake at 4:35AM Pacific Time isn’t beyond the realm of possibility. I’m currently surveying my existing telescope equipment (most of which hasn’t been out for quite some time) and hope to be able to video the resulting impact. Regardless, I’m planning on being awake to see it. Check out the NASA website:

NASA – LCROSS

I didn’t make it to this year’s SIGGRAPH, but I still try to keep up on my reading. There are several nice courses that occurred, and the guys over at the Real-Time Rendering blog were nice enough to link ’em for us. Enjoy:

Real-Time Rendering · SIGGRAPH 2009 Course Pages

Well, this isn’t quite amateur radio in the sense of ham radio, but it’s a cute and potentially useful project: a simple fm transmitter that uses only a single transistor, and is built “Manhattan style” on a scrap of PC board. If you’ve been looking for an excuse to try Manhattan construction, this might be a fun, low risk project that requires only the most minimal of investments.

BROADCAST YOUR PODCAST.

I am not really that much closer to figuring out why opposite sideband rejection is so poor, but I downloaded a couple of different SDR programs in the hopes that they might provide some diagnostic which might point more at the exact cause. Rocky still seems to be the best. PowerSDR seemed to work and has many cool features, but also seemed to pop and glitch occasionally. I also tried KGKSDR, which is a nifty program too, but which gave a glitch or two as well. I think the take away from all this is that sound cards suck.

But, a couple of interesting milestones with this: I decoded my first SSB signal with it yesterday (nifty!) and also my first PSK31 signal (Rocky has a built in decoder).

Oh, and I spent some time looking for a new scope. No luck yet.

So, I’ve had my Softrock 40 on the shelf for a while. When I’ve hooked it up, I don’t get very good opposite sideband cancellation. I think I see why, although I’m not sure how to proceed to fix it.

First of all, check out awesome WB5RVZ page on the Softrock Lite. The basic idea is that the Softrock runs an oscillator at 4x the center of the receive frequency (at least for the 40m version, the 30m is a bit different). The oscillator in the 40m I’ve got runs at 28.224 Mhz. It then runs two separate divider chains that create two (essentially) square waves run at 7.056 Mhz (which becomes the center frequency of the band received). Each of these is mixed with the incoming signal, and the result summed back together, which should result in an image of the entire band (subject to Nyquist sampling restrictions, naturally).

But what I’m seeing in my reciever is that I’m seeing each frequency at the opposite side of the carrier frequency (if I am trying to see a signal at 7.070 Mhz (say, a BPSK frequency), I also see the same signal on the opposite sideband at 7.042 Mhz.

It’s not hard to see why. I recorded a bunch of audio from it on my laptop, and plotted each sample as an X-Y pair. Have a peek:

If the radio were working properly, I’d expect to see a very symmetric pattern here, but instead we see an ellipse at 45 degrees. Not good. The thing is, I’m not sure what could be going on here. I’ve hooked an oscilloscope to the divider outputs, and seem to get what I would expect (although my scope is only a 20Mhz one, and the waveforms seem a bit distorted, which could be the scope or the radio). It seems unlikely that the two divider outputs could be that far out of whack: it’s just a set of cmos dividers. My best guess is the sloppy job I may have done on the trifilar inductor that I wound as a mixer. What do you all think?

I’ll try to get some oscilloscope screenshots up here later. i am still a rookie at using the oscilloscope, and haven’t been able to get the X-Y pattern that I expect yet.

Addendum: Here’s an example showing the lack of opposite sideband cancellation. I recorded some audio and ran it through my own spectrum rendering code, each horizontal pixel is about 20ms. You can see that the power in each sideband isn’t exactly even, but that we can clearly see the same signals on both sides of the middle frequency.

Addendum²: Here’s a photo of the X-Y of the two quadrature channels. I’m somewhat confused actually about the scaling: I am getting significantly more vertical deflection than horizontal, but that result seems to hold even when I reverse the channels. That obviously can’t be right. I probably have my scope configured in some stupid way. Oh well, this is how we learn, right?

Addendum³: Yep, something is definitely wacky. Here we are in dual trace mode. You can see the amplitudes are very close to the same, although the shapes aren’t very pretty.

Addendum⁴: AK6L sent me this link, which shows what I think the waveforms should look like…

Every few months, I read about some one who embarks and completes a homebrew CPU project. A few months have gone by, and here’s another. Someday, I really, really, really am going to have to do this myself.

Recently I decided to take on a very ambitious project to design my own microprocessor from scratch. A couple of things inspired me on this project, the first being a book I finished, Digital Apollo by David A. Mindell. This book details the design and engineering behind the AGC (Apollo guidance computer) and I was amazed to learn how well designed both the hardware and software were for it's time. The fact that it was designed completely with 3-input nor gates made it even more amazing. The second reason is the fact that several other people have done the exact same thing, built entire computers from basic TTL logic. A few blog posts have been floating around the internet detailing other peoples CPU designs, looking at these I knew it was something I could easily do myself and would be a very fun project.

via cpu_from_scratch [bradthx.net projects].

I have a bizarre fascination with algae. There is a lot of science going on with algae for use in food stuffs, in detoxifying industrial waste, and even as food. But my geek-itude is vastly exceeded by Jared Bouck, whose created an entire site about the cultivation of algae. I’m bookmarking this for later fun.

AlgaeGeek.com – Site News

Addendum: While reading the algae page on Wikipedia, I found a link to this book on identifying freshwater algae in the United States.

An annotated key to the identification of commonly occurring and dominant genera of algae observed in the phytoplankton of the United States

Well, today’s the day. For about the last year, I’ve been working away deep within the halls of Pixar Animation as part of a fantastic crew, and today (and for the next two weeks) you all can see the result of our efforts: the conversion of the original Toy Story and Toy Story 2 into 3D. For many, this is an opportunity to see a pair of classic films on the big screen, and in a new way that we all hope you will enjoy. Check it out, and let me know what you think!

‘Toy’ Stories in 3-D – Buzz Lightyear Finds a Dimension – NYTimes.com.

One interesting paper I read from this years SIGGRAPH paper on the creation of an interesting real life tagging technology called Bokode. Here’s a DIY page detailing an implementation. It’s really quite simple (and neat!) I might have to code this together.

Bokode @ Home – Recreating MIT’s bokode tech with everyday materials.

Yep, I’m actually at the NVIDIA (why do I type NVIDIA like nVidia? everything seems to indicate that it is all caps now, I dunno) GPU Technology Conference, trying to once again get into the swing of things with respect to GPUs. Sadly, almost everything I know about computer graphics (which is actually considerable) predates the ongoing revolution that GPUs have brought to the table. We’ll see if some of this sticks this time around. For the first time, I’m beginning to grasp the functionality of current machines, and see where the evolution is going such that I feel it might be worth committing a significant fraction of my (seemingly always shrinking) store of available brain cells.

It’s about time for the 2nd day keynote by Hanspeter Pfister from Harvard, to start. I was lucky enough to serve with Hanspeter on a SIGGRAPH Sketch committee a few years back, and it seems like he’s been busy since then.

I might blog more about what’s going on here, but you might as well track what’s going on using NVIDIA’s official conference blog:

GPU Technology Conference Blog – NVIDIA.