What Time Is It?

home brewing zulu time

de Bill K7WXW

IMG_1399

Amateur radio operators are obsessed with time. Maybe, more accurately, knowing what time it is right now. Usually we want this information in two or more ways or in two or more places. We want to join a net that starts at a fixed time, schedule an on-the-air meeting with another ham or see if our signal will get from point a to point b. We are always calculating the time somewhere else or the time difference between here and there.

We address time zones, daylight savings time (a particularly American oddity) and the-number-of-hours-between-here-and-there by using zulu time, also known as universal time. Zulu time is the same everywhere on the planet. There aren’t adjustments for daylight savings time or Nepal’s fifteen minute shift or time zones. Sunday at 4:00z is Sunday at 4:00z for everyone, everywhere. That makes it handy, for example, when scheduling a time to meet someone on the air and it doesn’t matter whether she is zero or six time zones away. Zulu time makes such things a lot simpler.

There’s one issue… I live in local time. To convert zulu to my time, I have a handy chart. Okay, it works but it isn’t handy. I wanted something that required less effort.

Which is why I spent yesterday and today designing a dual display clock. I decided to homebrew one after a web search revealed that my choices for a commercial version were either expensive: four hundred dollars for a LED dual display clock? really? Or fairly expensive and looking like, well, a cheap travel alarm. Seeing my options, I immediately thought, i can do better than that.

Parsimony isn’t always why I choose build over buy though it’s true that spending sixty or seventy dollars is less fun than coming up with a homemade alternative. Being cheap and fun-oriented, I found a kit clock and spent a couple of hours developing a dual display clock that uses two of them: deciphering schematics, figuring out what to modify, writing a list of changes, making a bill of materials, and ordering parts.

Puzzling out how to build something, making it, and then using what I’ve made is addicting. Home brewing almost always involves picking up some new skill, learning how to use a different set of tools or figuring out how to re-purpose other people’s castoffs. It is also a great way to connect with other people and hone practical skills.

IMG_1386Skills like working plexiglass. About a month ago, a neighbor put out a bag full of plexiglass scraps. She thought trash and I thought, project boxes, lots and lots of project boxes. The fact that I hadn’t ever made anything with plexiglass? how hard can it be? An internet search, a few online videos, and a visit to the local plexiglass supply store (did you know there are stores that sell nothing but plexiglass and stuff for making plexiglass things? me either.) and I was cutting and drilling.

The stand I made has a rough edge but the clocks look pretty cool mounted on it. Seeing my mistakes, I looked for a better way to make accurate drilling templates and cleaner cuts. That’s another thing I like about home brewing: when you find ways to make things work better, you can do something about it. If I buy that seventy dollar alarm clock-looking thing, it is what it is. Not so with my home built gear.

The home brewing process is the same whether I am soldering transistors or drilling acrylic. I specify what I want: what is this thing I am building supposed to do? I look to see what I can learn from what others have already done. After that comes design: the why, what, and how. The design products — schematics, drawings, parts lists, and so on —  are the basis for what I do on the bench. The last step is a non-step: when I have everything I think I need, I let it sit for a bit before starting.

That pause is important. Some of the best upgrade ideas happen after the design is finished and before soldering or drilling begin. New concepts float to the surface, along with oh my, that won’t work, will it? insights. I learned this from experience and saw good home brewers verify it; whether they are building a complex receiver or a simple box, they use the pause to catch mistakes and make improvements.

My dual time clock is on the shelf above my rig, doing what it is supposed to do. My investment? Six hours of design and build time, including a run to the hardware store, and about fourteen bucks. Mission accomplished: I filed my chart. I learned how to work plexiglass and a little about making and using drilling templates. Best of all, my new clock doesn’t work quite as well as I would like, which gave me an idea for an arduino based version with an LCD display. I just have to learn C first…

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Toroid Whisperer

learning patience one turn at a time

de bill K7WXW

On the bench in front wire coils of me is a half-empty printed circuit board in a vise, that I am not working on right now, and a just-finished one, which I am. It is supposed to be a QRP antenna tuner, a piece of gear that matches antenna impedance, which can vary, to an unchanging radio impedance. While a careful physical inspection of my work doesn’t reveal any misplaced parts, solder bridges or other assembly calamities, the tuner isn’t tuning. It is doing nothing other than being about as passive as any grouping of passive components I’ve ever worked with. Signal in, nothing out.

I have a suspect or two. This kit involves winding and installing toroid inductors, something I’ve never done before. The instructions are straightforward but the details are daunting: counting turns of wire around a tiny ferrite donut, with taps along the way and making three sets of overlapping windings. I find it easy to miscount turns or put a tap in the wrong place and getting the enamel insulation off the 24 AWG wire so the coil can be soldered into the board at five points is a real challenge.

Unlike most components — capacitors, transistors, switches, lights — that a kit builder buys in ready-to-use form, inductors usually arrive as a ferrite core of some sort and a bundle of wire. The sight strikes fear into the heart of a new builder: winding inductors has such a longstanding reputation for being difficult that there are folks who get paid to make them for hams that don’t want to make their own. I am not one of those hams. So far.

Since getting my license, I’ve built half a dozen small kits like this antenna tuner. When I figured out that I wanted to explore home brewing, it seemed better to start with gear that someone else had already designed and which works if built as instructed. Kits provide a gentle introduction (or in my case re-introduction) to schematic reading, soldering, electronic components identification and all the other things that make up the how of building electronic gear. Kits were a good entry point for me; though I’ve had to do rework on every project, I’ve not had an unfixable failure. Yet.

This time, though, I am stumped. After trying and failing way more than once to correctly wind and install the two inductors in this kit, I am starting to think it’s time to call a toroid whisperer. I didn’t account for left vs right handed winding consistently, so some of the wire ends finished on the wrong side of the coil. I miscounted (twice) the number of turns to a tap. I wound one of them correctly (I think) but didn’t get all the enamel insulation off two of the wires, which I figured out after I had soldered three others in place. I am not sure what other variety of mistake is possible but it seems likely I will discover them all before I get this thing to work.

Toroid winding is a lesson in accuracy, patience and letting go. Especially letting go. When I find it hard to admit that I’ve made a mistake — like I did while winding these inductors — I end up investing a lot of time and energy making less-than-well-thought-out repairs. Let me spare the new toroid winder some pain: trying to fix a badly wound toroid is always a mistake. Even if you manage to move the tap into the right position or whatever — which is hardly ever possible – the end result inevitably has some other kink or nick that will haunt you later in a much harder to find way. The only thing than a not-working toroid is one that sorta works. So… lesson one is admitting when I’ve bungled something, stepping back from it, and almost always, starting over from step one.

Winding toroids also teaches that accuracy is paired with patience. Twenty-two turns is not twenty-three or twenty-one-and-one-half. Ending up inside the toroid is not the same as outside. When you make an inductor, if you get it wrong, the circuit doesn’t work as it should or doesn’t work at all. And the only way to get it right is to work slowly, methodically, and patiently. It is difficult to count turns or get wire to lie flat if you are in a rush and easy if you aren’t. A well-made toroid inductor is a physical manifestation of accuracy borne of patience: it has the right number of turns going the right distance around the donut with the right spacing. It looks like it was done by somebody who cares about doing things right as surely as one that doesn’t says the opposite.

The inductor sitting in front of me, which I have clipped off of the printed circuit board, does not have this look. I can see where I rushed the winding: it isn’t evenly spaced and doesn’t lay flat against the toroid. Under a magnifier I can also see where I left enamel on two of the leads, which means they weren’t making good contact in the circuit and at least two spots where I kinked the wire trying to correct the winding direction.

After clearing the printed circuit board through holes of the wire bits and solder left when I removed the inductors, I set it aside and start clipping the wire from around the each toroid. I will work on them during tomorrow’s bench session, after I read the instructions again, study the drawings and track down a fresh roll of wire. I will set aside an hour for each, rather than fifteen minutes, and check all the connection points with a meter before I solder either of them onto the board. I figured out a way to check the windings for direction and count: make a photo of the finished inductor, print an enlarged copy, and tick off the windings with a pen.

I imagine that this approach will greatly improve the chances of my antenna tuner tuning. Maybe I won’t need the whisperer after all.

sight unseen

the habit of trusting people

de bill K7WXW

Almost every piece of radio gear I own, outside of hand tools, a DVM and the task light over my bench, is used. I love a good bargain as much as the next ham but that’s not my primary reason for buying other people’s stuff.

I recently purchased a magnetic loop antenna from a ham in Oklahoma, whom I will call Sam. He’s decided to focus on portable operations that don’t involve lugging stuff up and down mountains; the loop is “excess to his needs”. I love being outdoors, have been putting together a backpack-sized kit for portable operating, and enjoy mucking about with antennas. We are a match made in heaven.

We exchanged emails. Sam offered a fair deal and I didn’t haggle with him. Before I dropped the postal money order into the mailbox, I sent an email to confirm his address. He replied, confirming his address and letting me know he had already shipped the antenna. I mailed the money order.

Wait… he’d already shipped the antenna?

Sam and I have not met. We’ve not had a QSO, live approximately 1900 miles apart, and only know each only through our postings to an email list to which we both belong. We are, by conventional measures, strangers. Yet he sent me an antenna without having cash in hand and I did the same thing going the other way. Are we crazy?

Perhaps. I do prefer Paypal to money orders and I checked his QRZ page to be sure that an enterprising con artist wasn’t using an unsuspecting ham’s name and call sign for a scam. That was the extent my diligence, a fact which an younger version of me finds quite remarkable. But our email exchange was so straightforward that the QRZ bio page check just confirmed my gut call: this is a honest guy, I don’t need to to anything else.

Truth is, most of my ham gear buying and selling goes this way.  Sure, I’ve encountered a few cranks, grouches and one or two outright thieves but mostly I deal with people like Sam, honorable folks that follow the golden rule.  And the pleasure of encountering them, even if it is only through email, is one of the benefits that the exam study guide didn’t cover.

And each one still surprises me coming, as I do, from a world which valued besting the other guy above just about everything else. I am fortunate: as a ham, people like Sam happen along often enough to suggest a different kind of world is possible. I am grateful for the reminder.

Thanks Sam. I hope I have a chance to work you on 40 meters sometime.

meatloaf surprise

hbe2bw

part two: the price of not failing

de bill, K7WXW

I make awesome hard boiled eggs. Seriously. People love my hard boiled eggs. I could have a website or a cookbook cover devoted to them. It was not always so. I have ruined uncountable eggs. Under-boiled. Over-boiled. Hard to peel. Mushy. Chalky. Rubbery. Whatever sort of badly made egg you have ever eaten, I promise you I made one (or two or ten) of the same kind. I am the king of bad eggs.

Early on I was taught that failure was the province of losers and fools. My schooling and professional life were grounded in that idea. Badly-made eggs were not tolerated, let alone eaten. Good jobs, promotions and stock options were the province of people that did not make mistakes, at least publicly. So, like many of my peers, I became a guy that had to know how something was going to turn out before I tried to make it happen.

This approach got me the stock options, paid for with a bland, cooking-to-eat world. I seemed to be rewarded in direct proportion to how often I said no. Being a winner was equated with avoiding failure, which is synonymic for not taking chances. It worked, in the sense that I looked like the kid with the cake, but little that I did – designing a new product, cooking a steak, making a new friend – meant much because I was always pretty sure how things would turn out before I started.

Figuring out how to make a reliably good egg – or almost anything else – involves making some bad ones first. You have to try things, take chances. But if you can’t abide failure, you don’t risk bad eggs and you either give up eating them or have someone who makes a good egg make them for you. You do eat and don’t fail but live a bland life.

When mistakes are okay, an untasty egg is a provocation. You bite into one and you think, egg, water, fire. How hard can it be? You give free rein to curiosity and think about why and how and when (does it make a difference that I use an electric stove? how fresh are the eggs? how big?). You might even ponder big questions, like how does Anthony Bourdain do it?

Curiosity, the ability to think about the big picture and the willingness to learn from others is what makes good eggs, elegant designs, and lyrical translations. If all your projects have good outcomes – if you are almost always that kid – it is highly likely your recipes require little or none of these three ingredients. As I learned, stock options or not, it isn’t a very tasty sort of winning.

meatloaf surprise

part one: fulfillment and failure

de bill, K7WXW

The first birthday present I remember is a Betty Crocker cookbook. On the cover, two boys and one girl. The older boy, cake held high, is (of course) being admired by the girl. Her look says, he has done it again! He is triumph. I wanted to be that kid.

I remember cooking only one dish from it: Meatloaf Surprise, a ground beef encased hunk of ketchup-coated velveeta. Knowing my dad, who deeply disliked surprises, I am certain that my mom made a side of pork chops that night. I don’t remember rave reviews but I was quickly hooked on (sorry) the joy of cooking.bettyc_cookbook

I worked in kitchens in high school and college and owned a decent chef knife before furniture. Way before. Turning something (eggs, flour, water) into something else (bread) for people to eat was a big part of my life. A menu didn’t have to be complicated, or have fancy ingredients, or take five hours to prepare, to make me happy. A couple of well-scrambled eggs? Good enough!

Cooking taught me that making, transforming ideas into tangible reality, can be remarkably fulfilling. Cooking, photography, computer design, language translation, home brewing electronic gear; I fell in love with the process of turning ideas into stuff. I decided, what could be more awesome than that?

If the web is your guide, nothing. It is filled with triumphant boys showing off. Translations that sing, barbecue that falls off the bone, antennas that generate world spanning QSOs on five watts. It pictures a world in which stuff works. Amazingly well. On the first try. And if you come to believe this is representative of the process of making, you are going to be miserable.

I do not have one of those websites. Many of my meals are a reason for ordering take out. I have a zillion boring, blurry photographs, a resume with more than one spectacular product failure, and a junkbox of non-working homebrew gear. Stuff that works when I turn it on the first time is rare. Tasteless stew, overexposed photos and hundred foot long dummy loads are not. The truth? To be a maker is to be intimate with failure.

I can’t say that I learned this quickly or with any grace. I did not. For a long time, I let other people’s advertising determine the value of my making. I really wanted to be that kid, the one with the website who always got things right. Unable to abide the mistakes, screw ups, and disasters that are an inevitable part of cooking, designing, writing and so on, I turned it all into work and drudgery. I cooked to eat and made things when I was paid to do so but it certainly wasn’t fun, let alone awesome.

Meatloaf surprise? I don’t think so!

 

magnolias and antennas

magnolia_antennas

bending with the wind

de bill, k7WXW

The magnolias, one in the open, the other behind the scotch pines, are a couple of days from full bloom. Like most of the flowering trees around here, they happen in a burst. When they do, Amy harvests a branch or two for flower arrangements but mostly we enjoy them where they are.

This morning, however, there are two buckets of branches in the dining room, and on the porch, a pan piled with not-quite-flowering buds. My phone beeps while we are filling the second bucket: high wind alert. Old news around here. The gusts are sweeping flowers from trees all over the neighborhood and both magnolias will, I think, be bare before noon.

My antenna masts are two scotch pines, a birch, and a cedar. At this moment, the top of the birch is sweeping eight foot arcs, the cedar and pines, three or four. The dipole and end fed are, so far, moving with them. I finish helping Amy and head out to take care of the antennas.

At the base of each tree is an eye hook and a cleat. The pulley lanyard is cleated and the line that runs through it is attached to one end of an antenna. I can take the antennas down (and put them back up) without climbing. My original design included a tensioning spring between the eye hook and the antenna rope. Then I decided I was over-engineering things and didn’t install them. I watch the treetops bend, untie the rope, add four feet of slack and retie it. I move to the cedar and repeat the process. The gusts come and go. In the calm moments, the antennas dip toward the yard, forming deep, graceful curves. I’ve probably dodged losing one or both of them. Good thing I was home.

I spend the morning apparently working, but mostly I am watching the trees. The magnolias are holding up better than I expected. Of course. Trees are built to bend. On the way to more coffee I take the long route, through the yard. The dipole lifts and drops eight or nine feet in the middle. Amy is in the living room, turning blooms and branches into flower arrangements.

My antenna wasn’t built for this. If I hadn’t been around this morning, I’d have a tangle of wire in the middle of the yard rather than an antenna above it.  I am reminded that an antenna on paper is one thing, spanning my house, it is something else entirely.

On my laptop, a dipole is a wire of particular length and height, fed with more wire, and connected to a radio. EZNEC tells me it will have a certain resonant frequency and radiation pattern. A couple of websites help me estimate the cost, and so on. Before I get an antenna into the air, my problems have names like efficiency, loss, and noise. It’s all straight lines and numbers, like this diagram from the ARRL. Later, when 18 gauge wire, three or four insulators and a couple of pulleys are involved, the problems become unrelentingly physical: wind, tangled ropebranches, house-in-the-way. After all this time, I should not be surprised by this but I am.

Pines and magnolias move with the wind. In good years, they weave their branches around one another, grow over the house, drop some buds in a storm. In bad years, not so much growth, maybe some lost branches. They are not impervious to the weather – witness the ragged stump that is the top of one of the antenna-free scotch pines – but their organic responsiveness helps them survive most sudden or severe environmental changes.

Good designers can’t work slow as trees but they can mimic their way of adapting by asking questions. Sometimes obvious, what if something that isn’t part of the system changes? and sometimes not: how to get the feedline away from the gutter? Questions can be in the form of calculating or simulating or breadboarding or just going outside and looking at the trees. Whatever works! The important thing is asking. Don’t get lulled into thinking, there’s never lightning around here or when was the last time the wind really blew?

Good design isn’t organic like a tree growing, it is methodical and pragmatic. But the designer who blends good design practice with the willingness to not-know ends up with a tree-sturdy design: it doesn’t fail whenever the world outside isn’t quite as neatly organized as one’s lab notebook.  Which, by the way, is pretty much always. How do you not-know? Simply questioning everything during the design process is a good start. Your assumptions, the boundary conditions of the problem, your taken-for-granted knowledge? Put it all up for grabs, at least for a little while.

I used to begrudge the time required for this kind of questioning. git ‘er done!  was my motto. The reward for such parsimony was often a tangle of wire, glowing transistors and the like. Or when I made time for questions, I would dismiss the answers, as I did with the springs. Oh, that will never happen!  By now I’ve let plenty smoke out of stuff; I allow lots of not-knowing time.  My “dump the springs” decision suggests that I still need work on the pay-attention-to-the-answers-you-get end of things.

Late afternoon. The wind is a slow steady breeze. I was wrong, the trees aren’t bare. The porch is covered with petals but the magnolia is still mostly flowers. The dipole is drifting up and down a foot or two. I decide to give the wind another hour or two of free rein before taking the slack out and head to the basement to find some springs.

looking for trouble

part last: how to look

de Bill, K7WXW

Generally, when something in my shack stops working, I start with the basics: are the cables right? Have I turned on the power? Operator error is always the first hypothesis. When I’ve worked through the obvious stuff and don’t have a clue, I turn to the interwebs. Whatever I am trying to fix has probably been used, torn apart, repaired or modified by someone somewhere who subsequently wrote an email or blog post about it. A thorough search usually results in a pile of helpful files, bookmarks and contacts.lookingfortrouble2

Today, unfortunately, my first search didn’t reveal much so I went to plan b: asking for a little help from my friends.

Email lists and forums – what we used to call bulletin board systems and newsgroups – are my connection to hacker/maker/ham communities that always know more than I do about whatever piece of gear, technology, or software I am trying to make work, repair or hack. There’s a vast store of tribal knowledge in such places and on most lists, people are happy to help you if you do your homework and ask specific questions. In this case, I distilled what I needed to know into two questions, wrote a paragraph describing the symptoms and what I’d done so far, and sent it to a QRP list where I hang out. I write an email like this once or twice a month and the result is almost always helpful.

My email netted me a schematic of the base unit, good troubleshooting advice, and references to several articles about SWR meters. The articles helped me understand the theory and gave me pointers to other articles, along with the callsigns of hams interested in SWR meters and directional couplers. I used this info to do another web search and soon had a stack of articles, schematics, and photographs, more than enough to figure out how the WM-1 works and how to fix it.

It took a couple of hours to go through all the material. Along the way I learned a lot about directional couplers and RF measurement.  I was able to make some good guesses about nature of the problem, and come up with probable fixes. This is one of the benefits of I-have-to-fix-it-myself gear: figuring out what’s wrong with something is a great way to learn how it works.

I made a repair list and a plan for home brewing a new RF detector. I should be able to fix the old meter but building a new one will give me a backup and help me convert all the theory I’ve been digesting into a real piece of gear. Another perk of fixing-it-myself: the satisfaction that comes from using gear that I’ve repaired, modified or built myself.

I am glad I lost the habit of immediately replacing stuff that doesn’t work. My unusual meter spike has turned into a file of interesting articles, a repair project, a cool home brew project and a must-to-read list of RF design tutorials. I know a little more about SWR, RF power measurement, and directional couplers and I have had interesting conversations with three long time hams. If, three days ago, I was wondering about the wisdom of buying a flaky third-hand meter, today it appears to be a pretty good deal.

looking for trouble

part two: all the things it is not

de Bill, K7WXW

The sun is almost up when I let the dog out, make coffee for Amy, and sit down to check my email. I have three replies to my query. Someone sent me a schematic of the main board, someone else, three or four references to directional coupler designs along with technical data and photographs from three or four watt meters he built. The last email is a reminder not to rush through troubleshooting. I get my notebook.

My friend’s reminder is timely. Like most fools, I tend to rush in. Making a plan attenuates this tendency. My curiosity helps, too. Why doesn’t this work? is such a great question. I don’t just want to get this meter back on line, I want to know what makes it go. Troubleshooting is one way of figuring that out; maybe the best. Besides, I don’t have a spare meter. Until this one is fixed, I am without. Using the emails, schematic, and a little common sense, I make a list of things to do, then head downstairs.

After disconnecting the power and undoing the wing nut that holds the ground strap, I pull the desk away from the wall and start working through my list. I remove and test the coax cables and feedline. I examine the ground connections. Everything checks out. I make a note to look at the cables and connections at the outside panel, too. So far, though, no obvious problems.

I have two antennas, each going to a matchbox tuner. Between the rig and the tuners is a coax switch. The configuration is a bit complicated, so I take the switch out and test each antenna path separately. A basic troubleshooting rule I learned as an engineer: keep it simple. Complexity is hard to understand, let alone test. The corollary: change one thing at a time. Two variables changed means four possible outcomes, three means nine, and so on. Don’t make things harder than they already are!

I check the coax switch with an ohmmeter. It is good, too. I put the switch in line with the two tuners and test again. The antennas load on all bands. I make more notes. I’ve eliminated almost everything but the meter. I make sure I have cabled the radio correctly, push the desk back, and head upstairs. I haven’t completely nailed the problem down but I have eliminated a lot of possibilities. That is a good morning’s work; time for breakfast.

looking for trouble

part one: when stuff breaks

tshoot_040717

de Bill, K7WXW

While tuning through the 40 meter band, I notice the SWR meter spike and return to zero. Ten minutes later, it happens while I am not touching the rig. That’s weird, I think, but the net starts in twenty minutes. I don’t want to start taking things apart. I decide look into it later.

I drop to 80 meters, lower the RF power to five watts, and switch to AM. When I key up, the SWR meter goes to max and stays there. Adjusting the matchbox makes no difference. I move back to 40 meters. The same thing happens. Weirder. It worked ten minutes ago. Looks like I am taking things apart. With the meter out of line, I match the dipole on both bands. Putting it back in, I don’t.

Bad cable? I swap in a new one and check the old one with a ohmmeter. The new cable doesn’t make a difference and the old one is good, at least at DC. While I am switching the cables, I bump the meter and the receive audio gets a lot louder. I try to match the antenna again. Success. Could my third hand meter, an Autek WM-1, be the source of my woes?  I take it out of line and get ready for the net. For now, I can use the rig’s SWR meter.

I am embarrassed to admit this, but in an earlier life, I would have chucked the WM-1 and ordered something shiny and new. I was a busy guy.  Who had time to figure out why something didn’t work, right? In this life, I finish the net, put the meter on the bench and start taking the case apart.

I look for obvious problems: loose wires, cracked components, bad solder joints. The solder work is questionable and the sensing toroid isn’t glued down but there are no glaring (that is, easy to see) faults. I make a note to reflow the solder on all the connections and glue the toroid into place.

The instruction manual notes that unexplained SWR spikes aren’t anything to worry about. I speculate for a moment about career path of whoever approved the manual. There’s a schematic for the detection circuit but none for the main board and no explanation as to how it works. Not helpful.

I do a quick web search and turn up a few posts about the odd behavior I am seeing. Unfortunately, none include a fix or schematics of the base unit. I can’t call customer support; Autek disappeared years ago. I am not sure what to try other than cleaning up the bad soldering, so I go to plan usual: asking for help from people who know a lot more than me.  I send an email to the QRP list and set the meter aside for the night.

Grounding Bars and Bolts

Fine Tuning My Amateur Radio Station

de Bill, K7WXW

The ground bar is bolted to the shelf. The grounding straps of tinned copper braid between the bar and my rig, power supply and tuner, are in place. I am holding the last one, which will connect the case of the AC line filter to the bar, in my hand. The filter is on the floor near the wall outlet. But I can see there is a problem with the strap. Being four feet long, it will make a good antenna for any stray RF lurking around. Last thing I need is another entry point for noise, so I put it down and look for my notebook.

Other design decisions aren’t working out either. To get behind my rig, I have to move the desk. To move the desk I have to get out a quarter-inch socket wrench and unhook the copper strap that ties the ground bar to the rod outside.  Inevitably I need to crawl under the desk to retrieve the bolt after dropping it.  When I am done, I have to reverse the procedure, hopefully without the dropping-the-bolt step. This is not, as they say, an optimized process.

Sidenote: My friend Scott, N7NET, offers a tip for starting nuts in hard-to-reach places: dab a little Vasoline in the back of the socket to hold the nut in place until it catches the threads.

Apparently good paper designs often fail when they encounter real world voltages, screws, and transistors.  Spectacularly sometimes, too, as in what could you have possibly been thinking when you designed it that way? Mostly though, designs fail in small ways: a hard to reach screw or an oscillating amplifier.  Even good designers – and I am not in the category – have these problems. It is really impossible to know beforehand exactly how the thing we are designing is going to be used until someone is actually using it.

A piece of gear can’t get much simpler than a copper bar with holes drilled in it, a couple of standoffs, and a fistful of 4-20 nuts, lockwashers, and bolts.  Bolt the bar to the desk, secure each ground strap with a bolt, lockwasher, and nut, done. What could be easier? Something other than a ground bar, apparently.  The way I designed my system, undocking the main ground to get behind the desk is a giant hassle. The ground strap to the AC line filter is too long. And with a single bolt, nut, and washer per strap it takes two hands and two tools to make or break a connection. It all adds up to a list of changes that I didn’t know needed to be made until I actually put the ground bar together and tried to use it. And it also reflects a simple fact: paper designs, however carefully done, almost always need a tweak or three.

My first inclination is fix it now! Giving into this impulse almost always turns out, even in the simplest cases, to be a bad idea. My first unvarnished solution to a problem is usually (never) my best one. Sometimes it is not even my second or third best one. I don’t trash the first thing that comes to mind, but I don’t stop with it, either. I just see it as the start to a list of potential fixes to particular problems.

Even well-designed commercial gear doesn’t get through the design-build-use cycle without lists like this being written. When I was an engineer, we called them engineering change orders, ECOs for short. ECOs are another version of my lab notebook: what is the problem, what is the fix, what does it affect, how much does it cost? In the commercial world, an engineer has to write an ECO and get it approved by the people who live with the product and modifications made to it: manufacturing, marketing, testing and so on. Here’s a truth: those folks don’t like change. It mucks up their day. To get an ECO approved that engineer has to think through the problem he or she is trying to solve in a way that makes sense. Improvisation rarely wins the day.  Whether I was the designer or the design team manager, ECOs were my antidote for the spontaneous fix.

I don’t have a marketing department and I manage all the manufacturing and testing around here. The only person who has a bad day due to a poorly thought-out fix is me. That said, I don’t enjoy re-fixing a fix that didn’t work, so I address problems by following my homebrew version of the engineering change order process.

I start by looking at my original design. What was I trying to do? Did I miss something? I make a list of the problems and ask if any of them arise out of the original requirements. For the ground bar, ground straps should be as short as possible and in a star configuration. That requirement limits, among other things, where I can place the ground bar. If a requirement causes a problem and I can’t come up with a fix, I either live with it or I change the goal. Other problems come up because how I thought things would work is different from how they actually work. And, finally, there are the things I just get wrong. Now I have a to-be-fixed list, based on actual use, that reflects my original design goals.

Next, figuring out possible solutions. There are rarely more than three or four to consider. I just don’t have that many good ideas. As always, I write all this stuff down. Why? Mostly I don’t like having the same bad idea more than once.  The end product of this process is my homebrew ECO: a detailed lab notebook record of the what, why and how of whatever it is I am fixing, without all the check boxes and signature blocks one finds in the commercial version.

When I actually don’t know what might work, I go off to do some research. Maybe (almost always) someone has had this problem before. Or maybe a data sheet or application note will give me ideas. And sometimes simply setting the list aside for a bit does the trick. The list that comes out of this process will always be better than randomly trying something and hoping everything will turn out okay.

Now I have fixes I like. I start working through the list. The bolts are installed from the bottom of the bar with a lock washer and nut on the top side so they don’t have to be removed when I disconnect a ground strap. The  strap that runs outside is held with a wing nut instead of a nut now, so I don’t need a wrench or nut driver to take it off. The AC line filter is mounted to the underside of the desk with a six-inch, rather than four foot, ground strap. I can’t do much about needing to disconnect the outside ground every time I need to get behind the desk; no changes on that front.

After the fact, the fixes seem pretty simple and might hardly worth all the record keeping. Bill, that sure seems like a lot of work for a small problem. Couldn’t you just try something and see how it worked? Perhaps. Maybe though, simple fixes are simple because they are thoughtful and thoughtfulness is the result of writing down what one is doing and why.  It took me longer to write this post about the process than it did to actually do it.  That isn’t always the case. The chance of getting something wrong in a design goes up as the square (or worse) of the complexity. More parts, more chances for error. If that’s true, a process that includes time for making, testing and documenting changes seems prudent, even for a ham building gear in the basement.

I disconnect one of the ground connections to re-route it so it won’t block access to one of the antenna feeds. After checking everything against my wiring diagram, I plug gear into the new AC filter and the filter to the mains, then push the desk back against the wall. Getting behind the rig is a lot easier than it was two hours ago. Fix accomplished and later, when I am trying to remember why I did what I did on this project, I have my notes. It works.