brainwagon

I woke up this morning, and wanted to relax a bit before the day’s exciting activities (more on this later), so I noted that NOAA17 was coming up. I got out after the pass (which had a maximum elevation of under 15 degrees) was under way, but the audio sounded pretty clear, so I recorded the audio and got the following picture:

Because it was so short, I wasn’t 100% sure what I was staring at. The water at the lower right was (I suspected) the Gulf of Mexico, but I wasn’t 100% sure. So I got out my mapping software and plotted the path of NOAA17 along the ground. Sure enough, that seems plausible.

I should figure out how to plot the visible region for NOAA passes, so I can do this more routinely. In fact, I could probably merge this with my satellite prediction code to give the ground tracks of satellites more routinely. More stuff for the future!

Well, this morning I decided I wanted to get the K1EL keyer that I put together mounted in a proper aluminum case. The sad thing was, I didn’t really pay enough attention to internal clearances, with the net result that I did a pretty crappy job. I’ll probably try again sometime soon, but in the mean time, it’s at least functional, and is no longer at risk of being yanked apart.

Yesterday’s linked article about negative resistance oscillators got me thinking about the possibility of creating a radio where literally every component was made by hand. Okay, I’m not quite ready to make my own wire, but the zinc oxide oscillator that Nyle Steiner seemed like it was only one step away from reaching a reasonable approximation to that goal: instead of a transistor, it used an oxidized strip of zinc. Making potentiometers and capacitors isn’t that hard: the book Voice of the Crystal will give you some ideas about those.

The one element that seems like a specialized, manufactured bit of kit is the quartz crystal. But I suspected that even this could be manufactured, I just didn’t know where to look for information. But then I rembered that my ARRL membership included access to historical back issues of the QST magazine archive, going back to the time of World War I. Sure enough, a short search later uncovered a pair of articles from 1935 by Ivan Loucks, W9ON. Sadly, I can’t reproduce links to the articles here (they are copyrighted), but the first is from the Jan, 1935 QST, and is entitled Cutting Quartz Crystal Plates and the second from February is entitled Grinding and Finishing Quartz Crystal Plates. Combined, the two articles give a pretty good description of how quartz crystals can be cut from raw quartz, dimensioned and then ground and polished into crystals suitable for making oscillators.

This information opens up the possibility that you could make a radio transmitter with no premade components. I think that’s pretty interesting.

Addendum: Here is a history of the development of quartz crystal technology. It pointed me at an additional pair of articles about crystal control by J. Herbert Hollister from 1928 and 1930 in QST. From the article Quartz Crystal Facts, Hollister opens with this:

With just a year of the narrowband era behind us, we find the ranks of the quartz crystal exponents growing daily. At this time last year most of us thought crystal control was only some trick arrangement for the other fellow to play with and squander his money on. There were few, however, who did not envy the crystal controlled station with the beautiful bell-like note which was always to be found at exactly the same point on the dial.

The Spark, Bang, Buzz website has a lot of really interesting low cost electronics experiments involving homebrewing electronics components. Like making your own vacuum tubes, cathode ray tubes, and negative resistance devices. The last is very cool: using a heat treated piece of zinc, you can make a simple oscillator which was documented in the following youtube video. I’m gonna have to try this sometime.

The transmitter sounds a bit chirpy, but check out the schematic! It’s pretty darned simple, it’s hard not to accept a little chirp.

Courtesy of Bill Meara over at SolderSmoke, check out this link to the HF Beacon for MIT Atlantic Balloon Program. It’s a pretty simple 1.5w transmitter for 30m that could be built for about $25. It’s heart is a 74HC540 octal inverter chip, and uses two 2n7000 transistors. Very neat!

This is the greatest thing I’ve seen on youtube in at least a few hours.

Carmen got a cute little elf hat for Scrappy. He didn’t scratch or fuss too much, but neither was he especially happy. We decided to get a quick picture of him, and then gave him a little cat treat and let him get rid of his elf hat.

I must admit, I’ve been running Wordpress for quite some time, and for the most part, I’m pretty happy with it as weblogs go. But there are a couple of things that bug me about it. For one thing, it isn’t really very simple. In fact, it’s not just that it isn’t simple, it’s that it’s complexity seems far outpaced by its utility. Allow me to explain: Wordpress requires the installation of a bunch of fairly complicated software. It needs Apache (I have heard of it running with other webservers, but such a configuration isn’t well supported in my experience), PHP and MySQL. While the default installation is okay for modest blog installations like my own, to be able to support a decent load, there is the need to use caching plugins, perhaps offloading static content onto a different webserver, and generally a lot of performance tuning.

For instance, here is the output for running “siege”, which simulates a 15 simultaneous users trying to access my blog:


Transactions: 54 hits
Availability: 100.00 %
Elapsed time: 10.86 secs
Data transferred: 2.06 MB
Response time: 2.15 secs
Transaction rate: 4.97 trans/sec
Throughput: 0.19 MB/sec
Concurrency: 10.68
Successful transactions: 54
Failed transactions: 0
Longest transaction: 5.36
Shortest transaction: 1.53


10.68 transactions per second seem like it might be okay, but it’s no where near saturating the link speed. On the other hand, if you are serving mostly static content, you can use a server like thttpd. Here’s the output of a similar siege session simulating 200 simulatenous users:


Transactions: 4249 hits
Availability: 100.00 %
Elapsed time: 10.62 secs
Data transferred: 13.21 MB
Response time: 0.01 secs
Transaction rate: 400.09 trans/sec
Throughput: 1.24 MB/sec
Concurrency: 2.41
Successful transactions: 4249
Failed transactions: 0
Longest transaction: 0.27
Shortest transaction: 0.00


It’s running flat out: each page actually loads two files, so we get 400 transactions per second. The thttpd server haul’s major ass.

Okay, yes. The Wordpress blog is running all sorts of dynamic code, but 99% of the time, it’s producing precisely the same static content. We aren’t really getting a huge payoff for our huge decrease in available throughput. We could serve literally hundreds of simultaneous users with even modest hardware if we made better use of static content.

It seems to me that there could be a nice weblogging system based upon this rather simple observation.

I’ve posted links to the old time radio serial The Cinnamon Bear as part of my holiday preparations in years past. I updated this and got it working again. If you’d like to turn back your listening to a kind of neat 26 part Christmas story from 1937, try checking out The Cinnamon Bear.

One of the greatest things about computing technology is simply how much information is available to anyone who is interested. Technical reports, papers, and most importantly, open source software tools are all available to whomever wants them. This represents a significant democratization of technology. Major universities like MIT are even making entire college level courses available to the public.

It’s nice to see that Google is trying to do the same by establishing the Google Code University. Lots of good information available here.

Google Code University - Google Code

This website provides tutorials and sample course content so CS students and educators can learn more about current computing technologies and paradigms. In particular, this content is Creative Commons licensed which makes it easy for CS educators to use in their own classes.

The Courses section contains tutorials, lecture slides, and problem sets for a variety of topic areas:

• AJAX Programming
• Algorithms
• Distributed Systems
• Web Security
• Languages

Testing the Smart Youtube plugin for wordpress:

Jeff KE9V, over at KE9V.net is once again falling victim to pessimism about amateur radio. I can’t help but shake my head at the effort that we as hams seem to put into lamenting the impending death of our hobby.

It’s very strange. I can’t think of another hobby that spends as much time as we seem to in the following three activities:

1. Lamenting the impending doom of amateur radio, principally because so few newcomers enter the hobby, while simultaneously…
2. Grouching that all the newcomers in the hobby are wrecking the hobby because of their lack of desire to do things the way what we all learned, and yet
3. Spending all sorts of time trying to lure people into believing that our hobby is fun.

I prefer a different tactic.

If our hobby really was fun, we wouldn’t need to work at recruiting people: they would just happen naturally. We couldn’t keep them out of our hobby. If they don’t think amateur radio is fun, it’s probably best to assume that it’s not fun, at least for them. Something about the way we present ham radio to them makes them believe it isn’t fun. Many would argue that the man on the street just doesn’t understand what fun amateur radio is, but I would submit that the average ham doesn’t understand what fun is, or what the average young person would consider is fun.

Me? I just try to talk about the things which I think are fun, particularly things that can be done with minimal amounts of money and modest investment of time. I’ll leave the anxiety of the future of the hobby to others. I’d rather just keep plodding along, doing what I like, and trying to engage targets of opportunity who read about what I like as often as I can.

I just head that Endeavor will eject a small picosatellite (5×5x10 inches) that will test two different types of solar cells in the environment of space before it begins its deorbit maneuvers. I was interested in seeing if I could find any downlink frequencies for it, but haven’t managed to do so. I did find the following NASA page:

NASA - Pico-Satellite Solar Cell Experiment (PSSC)

While my blog has been dominated by radio related stuff lately, I do continue to be interested in lots of different subjects, including various topics related to computer security and codes. While scanning my feeds today, I found reference to this work, which I hadn’t seen before, but which I find interesting both for its security implications and its use of machine learning. Very cool.

Keyboard Acoustic Emanations Revisited

We examine the problem of keyboard acoustic emanations. We present a novel attack taking as input a 10-minute sound recording of a user typing English text using a keyboard, and then recovering up to 96% of typed characters. There is no need for a labeled training recording. Moreover the recognizer bootstrapped this way can even recognize random text such as passwords: In our experiments, 90% of 5-character random passwords using only letters can be generated in fewer than 20 attempts by an adversary; 80% of 10- character passwords can be generated in fewer than 75 attempts. Our attack uses the statistical constraints of the underlying content, English language, to reconstruct text from sound recordings without any labeled training data. The attack uses a combination of standard machine learning and speech recognition techniques, including cepstrum features, Hidden Markov Models, linear classification, and feedback-based incremental learning.

Tonight I took my wife, son and future daughter-in-law out to see Bolt, Disney’s newest animated feature. For extra bonus points, we went to go see it in 3D (yep, with the Real D glasses and everything).

I am somewhat skeptical about the long term viability of 3D. People seem to be highly variable in their reaction to the 3D experience: some people seem to find it hard to perceive any 3D at all, others seem to get headaches with even the most mild experience. I’ve rated my own reaction to be somewhat in between: I’m not immune to the eye strain, but I usually can tolerate it for a reasonable amount of time.

So, here’s the good news: Bolt looks great! And it’s a pretty nice family story too! Bolt is a cute young dog who is adopted by Penny. What Bolt doesn’t know is that he’s a TV star: he thinks he’s a super hero protecting Penny from the evil Doctor Calico. When Penny is kidnapped in the cliffhanger episode for the season, Bolt inadvertently escapes, and embarks on a quest to save Penny from the Doctor’s evil clutches.

The story is cute, the characters are cute, the jokes are funny, the look is amazing, there are some great action sequences (especially the first one): all in all, I think it’s a pretty fun movie, and my family agreed. The audience in the theater I was in liked it a lot too: I heard laughter at frequent intervals, and spontaneous applause at the end of the film. See it in 2D if you must (or can’t stomach 3D), but see it! It’s just darned fun.

Obligatory disclaimer: I do work for Pixar Animation Studios, a division of Disney. I suppose if the film does well, it could have some positive affect on my salary, but I have a feeling you’d have more of an effect if you bought me coffee.

Addendum: Here’s a clip from Youtube.