Archive for January, 2008

Perl

January 28th, 2008

My wife, Sarah, is a librarian. As she is fond of saying, she seems to start a career move with one idea in mind and end up doing something completely different. For example, a Biology/Education degree from undergrad became the foundation for a Library (and Information) Science Master’s degree with emphasis on young-adult librarianship. But, the combination of the MSLIS, a Biology degree, and the circumstances of my education (a big one), landed her a job as a “Science and Electronic Resources” librarian at a small college. Fascinating…but, what does this have to do with Perl?

One day when she was still a student, I casually mentioned that I had written a Perl script to fly through an enormous heap of data at work. “You know Perl?! We just talked about it in class today.” She thought it sounded pretty useful. I agreed. The things I do often lend themselves to what she does and vice versa. Time passed. They taught her some ASP.net/Visual Basic at the Engineering Library when she was a graduate assistant there.

Last Thursday, I was collecting my things to leave the office and my phone rang. It was Sarah. “So, my boss wants to know pricing information for 30,000 journals by the end of next month. My student worker is already tired and she hasn’t looked-up more than a few. All of the prices are in the same database. Do you think you could do that with Visual Basic?” I agreed that you probably could; but, I suggested that Perl might be better. She provided a list of subscriptions and we whipped up a quick script to do the job. Most of the time was spent trying to deal with the subscription-only nature of the database web site and managing the associated cookies. I’m sure this was a violation of a ToS somewhere… We let the script run when we went to bed…nothing like having a computer do your work for you while you’re asleep! As far as I can tell, it got every price that was provided…her boss owes me a pizza now.

She set a goal to start learning Perl over the weekend. On Saturday night, we went to a coffee shop on campus with laptops and did some more Perl lessons. (I used to poke fun at people whose dates consisted of writing code together.) She commented that it was “just like Visual Basic” but with different syntax. I’ve got a budding programmer on my hands…excellent (tent hands like Mr. Burns)… I also started teaching her emacs, which should further enhance that!

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NAQP and LoTW

January 16th, 2008

I entered the North American QSO Party CW Contest somewhat seriously for only the second time last Saturday.  I’m pretty happy with the results, especially considering that this score is 50% higher than my claimed score the last time.  I ended up with only 9.5 hours due to the 160 antenna situation.

Summary:
Band QSOs Mults
-------------------
160: 33 20
80: 279 47
40: 261 51
20: 66 29
15: 17 5
10: 1 1
-------------------
Total: 657 153 Total Score = 100,521

Ten and fifteen meters stunk…no big surprise here for this part of the solar cycle.  Although, I would liked to have done better on fifteen.  I took my off times (an hour each time) during the second and sixth hours of the contest.  I don’t know if I would do it that way again;  I had a really good run on 40 during the day.  I tried to work the second radio then; but, I haven’t mastered that, yet.  The first hour had the worst (< 60) rate.  I did much better after that.  My totals on 40 and 80 are within striking distance of the big guys like W9RE.  But, I just don’t have the firepower on the high bands nor the ears on 160 to do well there.  Of course, there’s still the whole skill problem, too…

Topband was a disappointment…I was hoping for about 40 multipliers and 100 QSOs.  I hauled an MFJ tuner up on the roof late in the contest to load-up the 80-meter dipole and feeder against a single elevated radial on 160 since I still don’t have that automated.  That could be a tonight project.  The noise on 160 on the vertical was 10-15 dB over S9.  Those 33 contacts were fought hard by me.  I need some RX antennas.  I talked to K9AN yesterday.  He suggested a K9AY loop.  I’m thinking about active verticals with a variable phasing combiner…less footprint.  We talked about pre-amps.  He wants to measure the NF of whatever I come up with out of J310’s from my junk box.

I requested a new LoTW certificate this morning since mine expired in January 2006.  Hehe…oops.  They protect your QSO integrity like Fort Knox!  In fact, they probably have a better idea of who you are than most credit bureaus.  I need to go through my logs tonight and clean everything up to get ready.  It sure beats QSLing, though…  I’m sure I’ll make a bunch of people happy in a few weeks.

Also came up with a great SDR idea yesterday that could be my new secret weapon.  It should be pretty easy to do, too.  No more on that until I get one working…

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Posted in computing, engineering, radio

How not to bargain

January 10th, 2008

Bargaining is one of the great lost arts among individuals.  It is the process of arriving, quite literally, upon the actual value of an item or service.  As I write this, it occurs to me that by shunning bargaining, stores have shifted that burden from the seller to the consumer…we now shop around.  Would a bargain-based economy better for the environment?  Anyhow, I digress…

I mentioned recently that I posted an old ThinkPad that I built from eBay parts on Craigslist.  A (Vietnamese) woman very enthusiastically contacted me about it because her old ThinkPad of similar vintage had been recently broken by her daughter.  This whole experience is probably worthy of a post in itself at some point.  But, on the phone, she said, “I see you have ‘$45 or offer’ on the ad…how much you take for it?”  Here, let me show you my cards so you know I’m bluffing.  I told her that I had about $45 in the computer and would like to get that; but, she was free to offer me what it was worth.  “Forty dollah, thirty-five dollah, thirty dollah?” she said.  I told her I’d take $40 for it.

So, what’s wrong with this?  Well, lots of things.

  1. Never ask the seller what they’ll take for it…you don’t find that out until the end!
  2. If you have the opportunity to see the item before buying, don’t start bargaining until you’ve seen it.
  3. Don’t start bargaining at the top.  I don’t think I’d have let it go for less than $40.  But, when she said $40, I can’t go lower than that anyway.  She’s blocked herself in at $40-$45.

Maybe this is a cultural difference.  But, I doubt it.

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Posted in communication, life

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

Ubuntu: Taking care of business

January 2nd, 2008

So, I posted an old laptop I have laying around on Craigslist.  While I was there, I checked out the Linux forum for kicks.  Someone posted something to the effect of “using Ubuntu doesn’t make you a Linux user.”  Following that were comments about “build it yourself” and “real Linux users use Slackware.”  This is the reason Linux is only free if your time is worthless.  I personally have better things to do with my life than to be endlessly building this and that and satisfying dependencies.  I’ve been a Linux user for about half its young life (the first kernel I built was 2.0.36)…and I think Ubuntu is the greatest thing to hit Linux since OpenSSH.  Like Mac OS X, it’s Unix-like without the fuss.  So, go on being snobs…I’ll be getting  my work done.

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