Antenna Guru

RF is not 'black magic' – It's Synthesis, Optimization, Analysis and Realization.

Tag Archives: Design

Making … Progress

It has been about three months since this progress report (of sorts)… so maybe it is time for an update.

Machining Precision Fixtures

You may recall the story about Rudy’s Big Idea (and parts two, three & four) and how I got started making my own prototypes. This effort has continued and expanded quite a lot. It might seem ridiculous for a highly educated professional to be turning cranks on a sixty-five year old milling machine, but there are certain subtle benefits—

  • If the ‘machinist’ has an idea what the prototype is supposed to do (s)he can often do the job just a little better and just a little faster. Making the first one of something is sort of like playing from sheet music in this regard.
  • It is nice to have a second pair of eyes take a look at the design. If that pair of eyes belongs to someone who is both an experienced designer and the prototype builder, so much the better.
  • Medium to large companies tend to have their own prototype shops but not the little guy, the entrepreneur.
  • Medium to large companies, in this economy, do not have excess capacity for onesy-twosy’s. At the same time, they need to innovate in order to survive.
  • Once you’ve made one, and it works, you often need to develop a process for making more. Who better to develop the process than an experienced engineer/maker?

So, this passionate little act of desperation is turning into a pretty purposeful enterprise.

Reality Checks

I did not expect it when I started on this path, but the world is full of “lone rangers” in little companies who get inspiration to try a new (to them) idea. Take, for example the patch array shown here. A fellow who had no microwave/RF design experience and no way to measure the interim results of his prototype wanted to get a “reality check” on his design. This was an extremely low-budget “moon shot” of an idea for this little company. You might even call it a “passionate little act of desperation…”

I am not exactly sure how he found me, so I’ll just chalk it up as one of those things. And it turned out that I had been through much of his unknown journey before. We had a couple of skype calls and I sent him a little memo outlining some of the gotchas and some of the things not to sweat at all. And this lone ranger rode a little more confidently off into the sunset. I hope we’ll meet again.

Unauthorized Tech Support

This one was also totally unexpected. Somebody gets a big idea for a product that does some little important job and then reports the data remotely, sort of like taking a blood pressure cuff and hooking it to the guts of a cell phone. Usually the person is a competent practitioner, someone who is experienced at engineering a system out of components available commercially, e.g. from DigiKey. They order their parts, build their prototype enclosure, debug the prototype and start the certification process when… BAM! They run into unforeseen problems.

Usually at this point in the process the company is too invested in the gizmo for wholesale modifications. Also usually, the designer (who is a competent practitioner, remember) has followed the reference designs and application notes provided by the component vendors pretty closely. The natural thing to do at this point is to reach out to the vendors for some tech support, and this is usually what these fellows do. The answer they get back is something like, “Well, you’ll have to move this component to the other end of the board,” or “Well, you’ll have to make the housing a little longer/wider/taller.”

Oh for crying out loud! Why not just start over? Why not give up?

Well some do, perhaps, but fortunately some don’t. A (growing) few are showing up here for what I like to call “Unauthorized Customer Service.” We don’t change the BoM in major ways; instead we figure out little tweaks and things to get that design to work.

Sure, I’d like to be in there at the beginning and get a bigger piece of the design pie on my own plate, but it is what it is, and it’s growing. Why walk away?

Man, Waddyacall It?

Finally there’s this issue of branding, also totally unexpected. It turns out that companies tend to shy away from contractors named, “Joe Somebody.” So, at minimum, I am told, I have to form either a corporation or a limited liability company (LLC). I toyed with “Antenna Guru” but it just didn’t produce many hits when I tried it out. My initials are “mwi” which look somewhat like a meander line if you tweak them a little. So the big question is, “What do I call this thing?” Should it be something like “Micro Wave Inventions, LLC” or is it better to call it what it is, “Mark W. Ingalls, LLC?”

Man, what-do-you-call it?

Nuggets from the World of Ideas

Once upon a time

There was a place where you could walk into a flowing stream, and if you knew what to look for, you could reach right down and pick up a piece of gold. I can imagine that copper, tin and iron once laid around in lumps.

In ancient Babylon and Sumer (and elsewhere) crude oil and tar flowed like springs up out of the ground.

Diamonds, rubies, emeralds, opals, turquoise, were all just pretty rocks…

…once upon a time.

Those days are pretty much all gone now, unless you count finding buried or sunken treasure.

…or are they?

The World of Ideas

Often in conversation, new friends will get around to asking me what I do. Or, knowing what I do, they will ask me how I do it. I have learned to pause for a second –or two– and look as if through an invisible door. In my imagination a metaphorical doorway from ‘our’ world to the world of ideas opens before me. Stepping through the doorway in my mind, I describe to them what I see.

Imagine a world where ideas lay around on the surface of the ground like rocks in a stream. You don’t even have to dig for them; you just have to meander around and notice.

“And I am not the only human being in that world,” I tell them, “Other people are there too, picking up ideas.

“Sometimes, I see people fighting over ‘big ideas’. I try to avoid those places. When somebody comes over and gets interested in taking over what I’m doing, I just give it to them and move on. I don’t want to get involved in a fight over one idea when so many of them are out there.”

Source: DC Animated Universe Wiki

Why Aren’t You Rich?

This is a natural question, I suppose, but one I didn’t think about before someone asked it the first time. It comes up a lot, though, apparently…

(Nygma discovers his office is locked and his nameplate is missing)
Edward Nygma: What’s going on here? Where’s my office? My door was right here.
Janitor: “Was” is right.
(Holds Nygma’s nameplate up and dumps it in the bin)
Edward Nygma: What’s the meaning of this?
Daniel Mockridge: What does it look like, Eddie? You’re out of here. You’re history. You’re fired. Comprende?
Edward Nygma: Have you lost what passes for your mind!? You can’t afford to do without me, Mockridge!
Daniel Mockridge: I can if you’re going to sue me for royalties.
Edward Nygma: I created the “Riddle of the Minotaur” game! This company’s making millions for my genius!
Daniel Mockridge: Competitron Software’s success didn’t come from the product, Nygma. Competitron has a corporate attitude. It’s strength is in the boardroom. The deal. The contract. Specifically the “Work for Hire” contract you signed.
(Shows Nygma a contract he tricked him into signing long ago)
Edward Nygma: You are a fool, Mockridge, if you think you can get away with this. Your amoral greed is no match for an intellect like mine!
Daniel Mockridge: Oh, yeah? Then tell me something, Eddie: if you’re so smart, why aren’t you rich?

DC Animated Universe Wiki

… so people ‘get’ the idea that cash follows creativity, but not necessarily in the same person. I feel like this– If I had to choose between pursuing ‘success’ or being able to go to that place, which would I choose? I guess the answer is obvious by now.

I’ve found myself feeling Edward Nygma’s pain a time or two, I won’t lie. But I learned there is more joy in going into that world than in fighting over who gets to bring an idea back from there.

Art·is·an …

OK, so the prototypes made last week are  working so far…







…which provided the motivation to sell some things and get myself a mill.

I have been studying mills for months now while waiting for the machinist from H-E-double-hockey-sticks to finally get ’round to my components. I started off thinking about computer control, but it was just too expensive to even imagine, plus there are plenty of small tasks that are better suited to the old-fashioned style manual turret mill. Just about all these things are made in China nowadays; nobody in this country wants to work that hard for that little money. The basic idea for the manual turret mill was conceived by Rudy Bannow, a patternmaker, in 1936. They say he was making a delivery to a customer when this idea came to him in a flash, so he sketched it out on a paper bag while sitting in his delivery truck. I decided I wanted one of Rudy’s machines.

US Patent 2,275,291,
“Machine Tool Operating at
Universal Angles in Overall Locations,”
Rudolf F. Bannow,
March 3, 1942 (filed April 4, 1939)

Rudy was an artisan who made patterns. He came up with one idea –one really good idea– that revolutionized the tool and die industry. Rudy invented the Bridgeport mill. There have been a few upgrades to his original paper bag sketch over the years: bigger motors, bigger spindles, stronger dovetail castings, and automation, but I wanted one of the originals. I wanted to be able to spend my time creating my prototypes with an artifact (something made or given shape by humans, such as a tool or a work of art). I wanted a tool that was a work of art.

This would require a pretty big chunk of cash, I figured $2500, because I would also need cutters, holding fixtures, measurement equipment, all the support stuff, plus there might be a significant freight charge… these things weigh a literal ton. All that I had to sell (all that I could afford to part with) was my HP 8753C. I was hoping to get enough out of it on Ebay® to (mostly) finance one of Rudy’s mills.

Make Like You Care

to make is to realize empathy

I saw this video today with a group of friends. It made me feel at once wistful and known.

Thanks, Jim

What Luck

Happy Friday the 13th.

“In the field of observation, chance favors the prepared mind.”

Louis Pasteur

Look’t that poor, tired sum’ bi’ch…

Haven’t posted for a while (ten days) ’cause I had a design problem’s teeth sunk deep into my derriere. Couldn’t crack it. So, I started to write a report explaining to my client why I couldn’t solve their problem, and something weird happened.

I perceived a solution.

Maybe I’ll discuss that later, but pro’ly not here. Here is where I want to talk about how it happened.

Last October is when this project started. I emailed a fellow who had liked my work from the past to let him know of my ‘availability’…  He had something… It was hard to see how to proceed, but when you’re hungry you’ll maybe try things. And as the searching, searching, searching, for the answer continued it seemed like I might not get ‘lucky’ after all.

“Let me tell you the secret that has led me to my goal. My strength lies solely in my tenacity.”

–Louis Pasteur

Heh. I quoted forty hours to survey known antenna designs and recommend the best variant. I’m way-y-y-y past that now. The trouble was that I had looked at perhaps six or eight published designs that purported to work the way I needed them to work. Some didn’t because of a quirk in my client’s statement of work. Some didn’t because they just didn’t. (Maybe I didn’t understand what the authors were trying to say, or maybe I did and they were just wrong.) In order to satisfy myself that they wouldn’t work I had to try really hard to make them work.  And I had wanted something to work. But nothing did, so I decided I had to give up.

I am on the verge of mysteries and the veil is getting thinner and thinner. The nights seem to me too long…”

–Louis Pasteur

I wanted to show the essential difference between a ‘wire’ antenna and a ‘slot’ antenna in a clear way. So I made a WIPL-D model of two loops of wire that were identical except for they way they were fed. One loop was fed in series and the other in parallel. My intention was to show that the parallel fed loop acted like a ‘slot’ antenna and the series fed loop acted like a ‘wire’ antenna. Here they are, the series fed loops are the first and third and the parallel fed loops are the second and fourth:

On the left we see the relative magnitude of the current density of the two loops at resonance. (Although the absolute current densities are different the relative distributions in the two different configurations are the same.) On the right we see the relative phase of the current flowing in the two loops at resonance. Here the two pictures look completely different.

Now look at the radiation fields of the two loops. Again, the series fed loop is on the left and the parallel fed loop is on the right. You don’t need to know a bunch of antenna lingo to see that these two pictures are very different. The difference has to be related to the relative phase difference of the current in the two loops.

Now, the wire antenna on the left and the slot antenna on the right are understood to be related theoretically by Huygen’s Principle, sometimes called the principle of complementarity. You can read about the theory of complementarity here and here, but I just want to quote a little slice from Wikipedia:

“From Babinet’s principle, a dipole antenna is complementary to a slot antenna consisting of a slot the same size and shape as a dipole cut from an infinite sheet of metal; both give the same radiation pattern.”


I believe Babinet’s Principle because it’s true. The trouble was, Babinet’s principle didn’t apply to these two structures because even though they were duals they were not complements! Again, from Wikipedia:

Let B be the original diffracting body, and B’ its complement, i.e., the body that is transparent where B is opaque, and opaque where B is transparent.

Everybody I know thinks about slot antennas this way. I used to, too.

He who proclaims the existence of the Infinite, and none can avoid it — accumulates in that affirmation more of the supernatural than is to be found in all the miracles of all the religions; for the notion of the Infinite presents that double character that forces itself upon us and yet is incomprehensible.

–Louis Pasteur

As this little golden nugget of Truth seeped into my brain I began to get this giddy feeling, like when in my dreams I can fly. I stood up and went to the kitchen for a cup of coffee and it felt like my knees might bend backwards and send me falling onto my face. I came back and sat in a different chair and just stared at the back of my computer like it was iconography.

And I knew I was going to crack it.  But I had received this epiphany during the very act of formally writing out my terms of surrender.

What amazing luck  chance  coincidence  providence…

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