Archive for the ‘education’ category

More on the fundamentals: a story and confession

January 10th, 2008

Anyone (does anyone actually read it with regularity?) who reads this blog is familiar with my rant about the “decline of the fundamentals.” Here is a story about a recent antenna project and how trying to circumvent the fundamentals came back to bite me…

One of the perennial problems for hams on small city lots (and worse, rental property) is the installation of effective HF antenna systems. My current lot is about 170’x 100’…substantial for a city lot. But, it has a 1500-sq-ft duplex plus a two-car garage. There are streets on two sides and the (above-ground) power line comes in from the corner opposite the streets. There are four large trees ranging from about 40-70 feet tall, approximately forming a 70-ft square (yes, I know 80-meter 4-square).

I recently installed a 40-meter dipole between two of the trees and an inverted-L for 160 meters between another pair. These were decent antennas, all things considered. I worked EU on 160 and could actually hold a frequency on 40 in the CW SS. I’ve had two 80-meter antennas since we moved here. The first was a killer…a 40-ft top-loaded vertical with lots of radials where the garden is now. But, the landlady and Sarah asked me (nicely) to remove my radials from their garden. So, I hastily errected a zig-zag dipole about 20-25 ft up between three of the trees.

Needless to say, I’ve never been real happy with the dipole. Furthermore, I only got four radials down this Fall for the inverted-L and the extras I laid on the grass sorta looked like a rat’s nest. I got to thinking…I don’t operate 160 that much. I had a rope in the pine tree at almost 60 ft for the inverted-L and I’d successfully shot a line into the big tree in the back corner to install my 40-meter dipole. I shot another line into the tree from the roof of the house. Great! I can put an 80-meter dipole at 60 feet!

The neurons kept firing…if I feed it with open wire, I can short the feeder and run it as a top-loaded vertical on 160. Brilliant. I can put the matching unit on the roof and use elevated radials (I can’t believe I’m saying this…but, it’s the only option for this installation) on 160. Dad gave me a roll of #14 THHN for Christmas (raw materials make the best presents). I went to a big box hardware store and picked-up the remaining parts for $15. I started cutting PVC pipe for spreaders with a hacksaw in the basement…hard work! Then, I remembered that the CubeSat shop is in the lab next to my office. A minute and a half with the bandsaw did what I spent a half hour on the day before. And, they looked better to boot. I built the antenna and hauled it into the trees.

Of course, using open-wire line, I had to do some matching. I measured the input impedance after the 1:1 balun (built with type-31 ferrite using a K9YC recipe) with my Autek VA-1. It’s L-network time! I figured there’s got to be an L-network calculator on the Internet that will save me a few minutes’ work. Indeed there is. I punched in the numbers and hit [calculate]. The component values seemed reasonable; so, I built it. Finding a coil form was a bit of a challenge. I have some Miniductor stock; but, nothing big enough. I tried a lot of things that I’m too sheepish to mention here before one day as I was leaving the office…I saw my coil form…lots of them piled-up against the instrument cases and cardboard boxes: poster tubes from conference travel. For good luck, I selected the three-inch tube that got stuck in the baggage handling system at O’Hare on the way home from Spring AGU in Acapulco… Actually, it gave me great pleasure to carve that up with the bandsaw.

I built the coil, added some capacitance, and triumphantly returned the relay/matching unit to the roof. I hooked-up the VA-1…and it was awful. The impedance wasn’t even close (it’s like 20-j200) to 50 ohms. I started clipping capacitors in parallel and it got worse. Then, I cut some off (the original design had three in parallel) and it’s got worse again. I’m up a creek! I went inside and had lunch. After eating, I carefully checked every joint and wire…good. So, I calculated the expected transformation given the parts. Hmmm…it gave me what I measured. I looked at the online calculator more carefully…

The calculator took the parallel equivalent circuit for the load, not the series equivalent circuit! I was in disbelief…who uses the parallel equivalent circuit unless they’re doing a calculation?! Apparently, the author did. Of course, it makes sense in retrospect…if I was writing an L-network calculator, this is the logical way to do it. I computed the parallel equivalent circuit, recalculated, and rebuilt. It hit almost dead-on 50 ohms.

It’s easy to see the lesson here: pay attention to details. But, perhaps the more important lesson is that the existence of ready-made design software does not justify ignorance of the fundamentals. Had I calculated the L-network by hand, I would have made the series-to-parallel transformation myself (or even better, let the VA-1 do it for me…wait, isn’t that how I got here?) as a part of the process. To quote the country song (out of context, of course), this was “time well-wasted.” I have a story to tell my students some day!

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Posted in education, engineering, life, radio

Five dangerous things you should let your kids do…

January 8th, 2008

I’m a huge fan of TED talks. I could watch them all day. This one caught my attention because I believe that it is important to explore your world, no matter how old you are. Gever Tulley (who’s not a parent himself, ironically) lists five dangerous things that children should do…

http://www.ted.com/talks/view/id/202

My two favorites are, of course, owning a pocketknife and dissecting appliances. This reminds me of a story…

Some friends had a “Turducken Night” party about week ago. The party split into two groups, one to watch Battle Royale and the other to play Catchphrase. Needless to say, we played the game. The game needed batteries and the door was secured with two self-tapping Phillips screws. Just as our hostess stood up, the woman to my left said, “Oh, I have batteries in my purse.” And I produced my Letherman tool saying, “I have a screwdriver.” The rest of the guests were astonished. Luck favors the prepared.

Are your children prepared?

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Posted in education, engineering

Implications of talk without knowledge

October 8th, 2007

Since I quit reading eHam due to the low SNR (signal-to-noise ratio), I’ve started reading news blog salon.com. Of course, whenever you enter a politically-charged environ such as Salon, you’re bound to encounter the same SNR problems as those elsewhere on the web.

In her piece Life Will Kill You, Katharine Mieszkowski writes

A cellphone is a microwave, and basically the reason your ear gets hot is that you’re warming it with a microwave.

Wrong! Your ear also gets hot because the phone is dissipating heat when it’s transmitting and because you’re trapping heat radiated by your body. My ear gets hot when I’m talking on a landline phone, too. Perhaps that should suggest something…

Do I believe that cell phone usage is 100% safe? No. But, I am concerned by the fact that people, especially in politics and the media, who have a tenuous grasp of science, are shaping policy opinions based on their junk science.

A project that my advisor and I are working on in South America got picked-up by the Weather Channel for a series about “extreme weather.” He showed me the broadcast recording (video file) of the story. The first thing I noticed when he played it was that the title at the bottom of the screen said, “Ionispheric Storms.” What? Yes, they spelled ionospheric wrong. “Well, that’s just a typo, ” you say. No, it is a failure of a system that is more interested in getting a story out than reporting something interesting or useful.

I’ve seen this sort of thing over and over on the War and Weapons Channel, the Discovery Channel, and others. I really can’t stand to watch TV shows about things that I’ve worked on these days because many of them are simply inaccurate. Why should I have reason to believe that the news or anything else is more accurate?

In a line of thinking I owe to statistician and information design expert Edward Tufte, real problems are messy and multivariate, rich and full of information and relationships. The more we learn about science, we should endeavor to make what we have learned more real, not more dilute. Everyone must know and learn more to do this. But, we will be rewarded for it.

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Posted in communication, education, life

Instructables, artists, and preservation of the fundamentals

June 16th, 2007

I took the car to the shop today for its annual preventative work. While I was waiting, I flipped through Popular Science. Wow, that magazine has changed (for the better) over the past few years (I haven’t read it in maybe 5 years).

They have a section called “How 2.0” that has skeleton projects, some with parts lists and vendors. Cool. We’ve come full-circle. It reminds me of the Instructables web site that I stumbled across a couple of years ago. The Popular Science section is really important because it represents a mainstream publication leading to the reversal of the “Decline of the Fundamentals” described here earlier.

One of the interesting things about this is that many of the characters leading the preservation of fundamental skills are artists. Not only are artists helping us see our world differently, they are helping us preserve valuable industrial skills. Sounds wierd to an engineer, doesn’t it?

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Posted in education, engineering, life

“You should have a reason for everything you do.” –K3ZO

June 15th, 2007

I happened to stumble across this K3ZO message mentioned on Don, K8BB’s, web site:

http://lists.contesting.com/archives//html/CQ-Contest/1999-09/msg00125.html

It’s perhaps one of the most insightful things posted to CQ-Contest during its 15-year life. Preparation and planning is important to success in most aspects of life. Why should contesting be any different?

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Posted in education, radio

The Decline of the Fundamentals

May 31st, 2007

Engineers everywhere shake their heads (or shudder) when a recent graduate new hire shows up bursting with knowledge and falls flat on their face when instructed to “do some engineering.” I oversee/mentor a few groups of seniors every semester in a Senior Design course that is intended to mitigate or avert the situation related above. So, I see a lot of painful mistakes. Many of the mistakes are things that I would consider fundamental, that is, for example, using a multimeter to measure the voltage “thru” a component rather than “across” it, or vice versa with current. (By the way, I did this once myself as a kid, before I knew Ohm’s Law and its physical meaning. I burnt-out the current measurement circuit in Dad’s meter trying to measure the voltage at a wall socket.) Short of more hands-on time in the laboratory, I began to ask myself why this was the case.

Abstraction is the concept that allows us to perform high-level tasks without understanding how the underlying process works. Technology is a fabulous example of abstraction at work. For instance, few people can really say that they understand how a computer works. I’m an EE and I have a pretty good idea of how they work; but, I wouldn’t necessarily be comfortable trying to develop a computer from scratch (at the gate or transistor level). So, this brings us back to the multimeter. At one time, the volt meter and ammeter were separate instruments; so, there was more distinction between the measurements. Is this a failure of abstraction or a failure of understanding? It does represent a fundamental failure to understand the physics: the idea that current is the flow of charge and that voltage is the potential (to do work) between charges. But, if no effort is made to stop during the education process to say, “What does this tell us about the physics?” these failures will continue. (Part of the problem is that some of the instructors have a tenuous grasp on the physics as well.) Abstraction remains an important concept, though, permitting sophistication.

The other problems are mass-production and “cheap” information. It used to be that if you wanted to get a job, you needed to know how to do something. (See The Cluetrain Manifesto for more on this sort of thing.) It is rare that one person knows and understands how an entire product is designed and constructed. This is the genius of Henry Ford and friends. It’s efficient for business, but not so good for humanity. Furthermore, we tend to let our knowledge exist in and be cataloged by Google these days. It does not occur to most of us that it might be good to own a hard copy of information that pertains to our knowledge of a product, process, or procedure. Google offers pin-point precision at the expense of “situational awareness,” understanding how the information fits into a greater context. Think of how many great discoveries may slip through the cracks of a web search!

The final culprit is assisted computation. There is a certain amount of insight gained from struggling with a mathematical expression for a physical relationship. There is even more insight in quick approximations. The art of approximation is dying. Dr Donald Milks taught my undergraduate Statics course. He was of the old school. I used to race him in solving example problems in my head using approximations. He almost always won. The few other students who were interested enough dutifully punched away on their calculators. I usually beat them, though. Dr Milks valued good hand-drawn figures, too. Indeed, the act of drawing, too, yields insight about a problem. I miss that.

Technology and abstraction allow us to solve progressively more difficult problems in science and engineering. I embrace that. However, we must take care not to lose sight of the fundamentals. For with time, the most advanced problems may prove intractable when no one understands why we want to know the answer.

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