Archive for the ‘engineering’ category

Trials and Tribulations of a Geriatric Electronics Specialist

February 6th, 2010

geriatrics

I have an old radio problem.  Make that three old radio problems…err…problem radios.

My first used radio was the TS-930S you see in this picture.  It’s been good to me, and I’ve tried to reciprocate, although I am a contester.  It hasn’t quite been the same since I put the third set of PA drivers in it and repaired the power supply.  Something deeper must be wrong.  I found out tonight that something deeper was indeed wrong, in the form of not one, but two, exploding electrolytic capacitors.  At least I had one of them in the junk box, but I figured I was pushing my luck and came up here to the shack to blog instead of blowing up another one.  The power supply pass transistors were assuredly toast since they were riding high at 40 volts—got that fixed.  But, it still pops caps.  Crap.  Something is amiss in the final PA bias circuit (MRF-422).  I don’t think that the ratings of the MRF-422’s have been exceeded.  So, it should be a matter of diagnosing the bias circuit and getting back on track.

The TS-700S at right is my most recent used find.  It’s in practically perfect cosmetic condition.  But, during the ARRL January VHF Sweepstakes, the output power started fluctuating before finally going to zero.  The T/R relay driver transistor failed, but there’s still something else going on—it looks like an ALC issue of some sort.  I did just finally find a service manual for this guy and that should help the diagnosis.  Although, the service manual is unusually vague about the purpose of some of the control signals that are passed between functional blocks.  This might take a while, too.

The other TS-930 actually works, except only on 40 CW.  On the other bands, the PLL unlocks.  KA5IPF suggested that I tweak the master oscillator to keep it off the ragged edge of unlock.  I’ve done that a few times and can’t quite hit the sweet spot.  My next plan is to pull the PLL unit out (a real pain) and reflow all the solder joints on the board since it comes from the early era of the TS-930, when cold solder joints were common.

I’ve pulled the FT-840 out to be the second radio for bands other than 40 CW.  And, I’m missing the Sprint tonight to spend time with my wife since I spent the better part of the afternoon tracing through the TS-700 and hooking up the FT-840.  Fortunately, I have the FT-840 configured as a drop-in replacement for a TS-930—this is in no small part due to the fact that the PIEXX boards use Yaesu-style BCD band-decoders—so, I can plug right in with the appropriate adapter.

How Things Work

January 3rd, 2010

flying

As a part of my employment, I occasionally have the opportunity to talk to students in the local schools about my work.  I tend to treat these talks as a “choose-your-own-adventure” for the students, weaving some of my stories and demonstrations into the discourse along the way.  The students love it because they are participating; the host teacher and I don’t get bored hearing/saying the same thing over and over.  It’s a win-win for everybody.  Plus, I get to explore the creativity, imagination, and mental models of the students.  This is one of those stories.

About a month ago, I was talking to some 8th graders about electromagnetic radiation and radio.  When we were talking about the speed of light, I asked the class if anybody knew how GPS works.  One student raised his hand and I called on him.

“You type in the address of your destination.  Then, a satellite moves over that spot and it directs you in.”

These answers always surprise me.  “If there was a satellite for every GPS user, ” I asked, “how many GPS satellites do you suppose that there are?”  He speculated that there had to be quite a few.  Then, I asked, “How much do you suppose a satellite costs?  Do you think that would be cost-effective?”  The discussion continued for a minute or two until we converged on the time-of-arrival method.

Later, I was reminded of watching the movie Enemy of the State with my dissertation advisor when we were on a field installation trip.  We chuckled when a spy satellite was repositioned to track Will Smith’s character.  It’s a good movie, but it’s a bit fanciful at times.  The movies might be the most education the average person gets about satellites—a sobering thought.  On the other hand, there are dozens of things (such as biology, I tell my wife, who did her B.S. in biology) that I treat like black boxes.  There’s just too much to know about to have specialist understanding of it all.  How much is enough?

Since today is Epiphany Sunday (the day that celebrates the magi visiting the baby Jesus) in most Christian churches, I also add the following:  A week ago when we were home for Christmas, I was telling Dad how I always enjoy questioning students about how technologies they take for granted operate to cultivate their creativity and curiosity.  I mentioned the model of the GPS satellites hovering over destinations.  He quickly replied, “Well, that’s how the wise men found Jesus with the star, isn’t it?” These people keep me on my toes!

Projects, projects, projects

December 11th, 2009

There are lots of projects going on here at the ranch and I’m not sure where to start. So, I’ll make a dreaded bullet list. A lot of this stuff has been a long time coming and I haven’t even had to spend much money on it, just time.

QSLing:

  • Some PJ2/K8GU cards are still in the queue since USPS didn’t like the “gift” (a laser-engraved poker chip) I was including with them—need to get padded envelopes.
  • No KP4/K8GU cards have been replied to since I don’t have a card design yet. This will be a photo card.
  • Plan to have all direct QSLing caught-up by the New Year.

HF station:

  • QRV on 80/40/20 with full SO2R.
  • Right TS-930S still needs a new set of MRF-485 drivers (although it puts out a few watts).
  • Left TS-930S needs PLL/master-oscillator alignment so it will go to bands other than 40 meters.
  • Built IK4AUY 2N5109 push-pull preamp from QEX article—needs finished and tested.  Have enough parts to build two, but might go with the simpler W7IUV design for the other instead.
  • Plan reduced-size K9AY for 80/40, maybe 160.
  • Plan W3NQN RX filters to go on the K9AY ahead of the preamp.

VHF/UHF station:

  • Wired in Jones plug(s) for the rotator.
  • 50-MHz transverter project is stalled awaiting parts orders (SM caps and toroids).
  • Do a planning cost analysis of 50- and 432-MHz transverter costs vs buying a used FT-817.
  • Ordered W1GHZ 903- and 1296-MHz boards and kits with W8ISS.
  • Plan PAs for 903- and 1296-MHz transverters.

Computers:

  • Bought new keyboards and mice for sakhalin and formosa.
  • Thanks to the generosity of a friend, sakhalin now has two Seagate Cheatah Ultra320 10-krpm 36-gB disks.
  • Added the old 1.7-gB IDE disk from the “ham computer” to sakhalin so I can still run TR.
  • Added the extra RS-232 ports from the “ham computer” to sakhalin for rig control.
  • In the process of configuring sakhalin to triple-boot Windows 95 (aka MS-DOS 7 for contesting TR), Windows XP (so I have it), and Xubuntu.
  • Plan to migrate formosa user data (not much of it) to sakhalin.
  • Plan to convert formosa from Xubuntu to OpenBSD using 20-gB drive from sakhalin, plus 120-gB already inside.
  • Plan to migrate crete server contents to formosa.
  • Plan to convert crete back from Ubuntu Server to “ham portable computer” running Windows 95 (aka DOS 7).
  • May run a network drop to the basement to use crete in the shop.
  • The MacBook (vieques) still just works.
  • So does the OpenWRT box (home).

And that’s just the hobby stuff!  Well, most of it.

Hacking Engineering Education

October 25th, 2009
Bell System Manhole Cover

Bell System Manhole Cover

While browsing my local public library a few weeks ago, I stumbled across the book The Best of 2600: A Hacker Odyssey by one Emmanuel Goldstein.  Despite my own youthful adventures (perhaps chronicled in a future post) with computers and networks, I never got into reading 2600, probably for the better.  But, the book represents the best of the magazine and it’s worth reading through more mature eyes.  Why?

The hackers are playful.  They are creative under duress and with limited resources at their disposal.  They tell stories.  They share mental models of the networks they’ve compromised.  They are the explorers of the networked world.  They are social—they understand that networks connect people.

Of course, this assessment glosses over the criminal and arrogant aspects of hacking.  But, the concepts of exploring, building, and sharing knowledge and models are valuable skills for the innovators of tomorrow.  Perhaps we can learn something from the hackers?

Homebrew Fire Ring

October 3rd, 2009
Homebrew Fire Ring

Homebrew Fire Ring

At our last place in Urbana, we had our “space” in the back yard, sort of an outdoor living room.  The new house lacked that until recently.  We obtained a rusty old truck tire rim from some of my not-too-distant kin in the tire business.  I picked-up a rust-buster abrasive head for my angle grinder and went to work on the rust and caked-on road/tire grime.   Some degreaser and a rag helped get most of the rest of the grime out.  Then, I painted it with flat black grill paint for a classy rust-free look.

Total cost: about $10 plus three hours’ time to finish the rim.  The neighbors probably think we’re rednecks.  But, who cares?  We had the first of hopefully many pleasant fires tonight.  Besides, how many chimenea owners had the pleasure of busting rust off of a 35-pound hunk of steel?

Interesting trivia:  In the past three posts (inclusive) with photographs, the on-going projects are pictured.  That is, in the workbench photo, the antenna mast and rotor control box are shown in the lower left portion of the image.  In the rotor photo, the unfinished fire ring is under the rotor.  Then, this post has the finished fire ring. The beat goes on…

The Workbench

September 11th, 2009
The Workbench

The Workbench

I finally got my workbench set up a the new place.  Total cost: $10 (for an IKEA countertop from the AS-IS department—the only reason we go to IKEA)  The workbench superstructure is recycled from the crate in which they moved our china cabinet.  Now it’s time to sort through the junk box(es)!  I’d like to pick up some more test equipment, but I’m (clearly) out of space for that at this time.

» Read more: The Workbench

Reading other peoples’ poetry

May 17th, 2009
Mobile Carwash, San Juan, PR

Mobile Carwash, San Juan, PR

This entry is dedicated to my brother Seth, who recently bemoaned his declining creativity.

Seth makes a lot of interesting points about things that may or may not have affected his creativity—resource-poor, idea-rich; lack of peer pressure (this one is brilliant, by the way); risk-averse grown-up life; personal disorganization; time-poor; adverse affects of education; etc…

I would like to counter that none of these things necessarily impede thinking creatively, although they might impede acting on that thinking to various degrees. At some earlier point in my life, an English teacher proposed that in order to be a good poet, you had to read other peoples’ poetry. I scoffed at the idea at the time. After all, poets disregarded normal rules of communication. What did it matter that you read anyone else’s work?

It turns out that it matters a great deal. Poetry forces you think about things in a different way. For me, the idea of poetry is fascinating: a “word bargain,” as another teacher once described it. But, have you ever read poetry? It’s like medicine: it might be good for you but they can’t hide the true flavor. I digress. The good news for scientists, engineers, designers, tinkerers, and people who just don’t read, is that we are surrounded by wonderful poetry written on everything we see and do. We must merely notice it and read it.

Carry a notebook, carry a camera, look with a critical and curious eye…

Are you reading other peoples’ poetry?

About the photograph: A mobile carwash system at Parque Barbosa in subbarrio Ocean Park, barrio Santurce, San Juan, PR. The red van contains a large polyethylene water tank and a pump. What problems does this solve? Create? Note locally-available materials. Definitely OPP.

» Read more: Reading other peoples’ poetry

Dissection

May 11th, 2009
DBS Downconverter

DBS Downconverter

I found an old satellite TV downconverter in the garage today. It drew me in and compelled me to disassemble it. One of the wonderful aspects of microwave circuits is that classical layout strategies persist. This board has a single layer of traces over a ground plane: everything is laid-out in one plane, quite visible and tangible (perfect for learning, I might add). The waveguide that feeds the antenna has two probes that bring the signal onto the board. You can see the I and Q channels and their respective LNA stages, the dielectric resonator oscillator in the center of the board, hairpin filters, mixers, bias lines and matching sections. Beautiful.

» Read more: Dissection

Automatic

February 21st, 2009
Oscilloscope

Oscilloscope

The oscilloscope autoscale button is a perpetual headache for teaching staff in the Senior Design Laboratory.  Students often think they have a funny-looking signal, when in reality they’re just amplifying noise and something else is wrong with their circuit or measurement.  Why?  The autoscale adjustment reports the timebase and channel amplification/scale data in a corner of the display, not through intervention by the operator.  Is this bad ID?  Or, just poor ID for learners?  What mental models do the students have of digital oscilloscopes versus analog ones?

Where do we draw the line between automatic and manual in engineering education, between historical and cutting-edge?  How important is it to understand a measurement versus knowing how to make a measurement?  Should students learn on analog oscilloscopes so they understand the functions of a digital oscilloscope?  Should we teach the Smith Chart despite the fact that nobody uses them as calculation tools anymore?  Yet, they are one of the most common ways to present impedance information in datasheets and on network analyzers.

Engineering is causal.  History matters.

» Read more: Automatic

Resume of a Master Dumpster Diver: the Early Years

February 21st, 2009
Dumpster

Dumpster

With transition imminent in our lives, I have begun packing up some of my things that I don’t use much right now. It’ll save some time and headaches when we finally figure out where we’re going and begin the moving process. Coincidentally, my good friend Matt recently moved cross-country and elected to dispatch the majority of his tinkering resources via Craigslist. You see, Matt and I share a common vice: we are master dumpster divers.

I was reminded of this reality as I have been trying to center myself with respect to what’s important in life last week week. I have a lot of stuff, frankly, an embarassing amount of stuff. And, although I use a surprising amount of it, I really don’t need it. But, this post is about collecting the stuff, not getting rid of it. I’ll save that for a later post.

As I began sifting through some of the goodies tonight, a confluence of thoughts began to swirl in my head. I’ve had resumes and vitae on my mind for quite a few months now since I’ve been looking for employment (if you hire engineers or scientists, particularly for RF/signal processing/remote sensing/upper atmospheric/space research and development, I’m your man). And, I was poking through the rubble of my home “office,” which is actually my office, hamshack, and workshop, plus Sarah’s desk and books and the place that Sarah and I cram stuff into when company comes. Suddenly, it hit me: my entire resume can be read through my collection of odds and ends.

Dumpster diving, to borrow the analogy from Nelson Muntz, is like “kicking butt” in the sense that it might not involve any kicking at all. Likewise, you have to get to the stuff before it gets to the dumpster. This is the first rule of dumpster diving: Know who to ask, how to ask, and when to ask. The second rule is don’t get greedy. I learned both of these rules at a tender young age.

You see, the house I lived in between the ages of three and nine was next to the Village of Millersburg’s street department garage. Of course, this was a great boon for a child of my age to see all of the equipment and workers coming and going. Mom and Dad may remember this story differently; but, this is my recollection.

Although I was fascinated by all aspects of construction work, the one thing that I obsessed over more than anything else was signage. Some kids are experts on dinosaurs, I was fascinated by road signs. I coveted the road sign poster on the wall at the BMV. Mom had inquired about obtaining one for me to no avail. The other thing I coveted was a road sign or two of my own. A friend had a stop sign in his room; but, I was looking for something more exotic, maybe a yield sign. My poor mother worked some connection she had at the Street Department to get a discarded sign. She told me that we could go down to the sign depot and pick one out in the morning, which was probably a mistake.

I rose particularly early the next morning and, after locating the sign depot, collected a few signs for myself. When you’re a kid, street signs don’t look big and heavy on their posts. But, when you get up close, they rival your personal geometry. So, I left a trail of signs I couldn’t carry back up to the house. I don’t remember the details of what happened next, other than that we had to return all of the signs and get “approved” ones. I hope somebody thought it was funny; goodness knows I learned a lesson that day about the difference between dumpster diving and theft of city property.

A few years later, Mom had an antique dealer come through the barn behind the house and the signs caught his eye. She let him have them for a song. I was incensed at the time, although in retrospect, it was probably better to not profit too much on them.

The basement of the Inventor’s Hall of Fame once hosted an area where kids could dismantle old hardware. We were fortunate to visit when some racks of AT&T Long Lines hardware had been recently donated. I think I carried a half-dozen plastic sacks of relays, waveguide, transistors, meters, and other assemblies out of there that day. Although I have sifted through most of that by now, the juiciest pieces still remain in my inventory, ready for use. I still don’t think that the docents knew what hit them when the budding master dumpster diver rolled in.

Although I dabbled off and on in the barter of used electronics and such in high school, the dumpster diving began in earnest again in college, where I met guys who weren’t afraid to actually climb into real dumpsters to fish things out. Those were good times. Most of the stuff we pulled out of the dumpsters was building materials, which we used to spruce up our living spaces. Blocks from a demolished (the Young Building of Philosophy and Relgion, a grievous sin against architecture and HVAC) academic building allowed us to put an “upper deck” couch behind the regular couch in our apartment for stadium seating. This was great for watching movies, or at least watching my roommates play Mario Kart 64 with their pharmacy notes on their laps…right.

One of the other great successes was DuddiNet and the Tower of Power. I dragged an 8-foot relay rack (rescued from the scrap heap at a summer job) into my dorm room and filled it full of computers and networking equipment. I asked the university IT people if they had any leftover rolls of CAT5 cable and they gave me as much as I wanted. We pulled our own network in the dorm. At that time, the dorms were 10baseT with hubs. So, it was a real bottleneck if you wanted to move some data (use your imagination here) around. We put in a private switched 100baseT network that connected four rooms on two floors.

In more recent years, I’ve scored some terrific stuff just by paying attention when spaces are being cleaned-up. For instance, that’s how I got my HP vector voltmeter and my oscilloscope. And, indirectly, through Dad, it’s how I got some more Greenlee punches and a set of metal-marking stamps. Anyhow, in order to protect “sources and methods,” I’ll decline from disclosing too many details about my more recent activities…I haven’t swiped anything from a forbidden dumpster, though. Promise.

» Read more: Resume of a Master Dumpster Diver: the Early Years