Antenna Guru

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

Tag Archives: Prototype

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?

Self-made Man

Self-made men are the men who, under peculiar difficulties and without the ordinary helps of favoring circumstances, have attained knowledge, usefulness, power and position and have learned from themselves the best uses to which life can be put in this world, and in the exercises of these uses to build up worthy character. They are the men who owe little or nothing to birth, relationship, friendly surroundings; to wealth inherited or to early approved means of education; who are what they are, without the aid of any favoring conditions by which other men usually rise in the world and achieve great results.

Frederick Douglass

I’ve been struggling to make it lately– economically, intellectually, emotionally, …as a man. In particular, I’ve been struggling to actualize an antenna concept that may be great, or just pretty good, or possibly…

It’s just plain crazy.

To find out which it is, it would have to be built. I wasn’t confident where and how to tune it, so I designed extra flexibility into the components. Trouble followed. The toolmaker took plenty of his time and my money to produce parts that didn’t work all that well. This was partly my fault, because I let him source some of the materials and parts that should have been flat were not. I ruined the first one trying to get it to work, and sample two was ugly and its performance marginal. So the results were ‘mixed’.

I could give up or I would have to build more prototypes.

The only tools I had to machine the prototypes were my six inch Craftsman Mk 1 Lathe, my beloved Bosch jigsaw, a Dremel tool, a Palmgren vise and an assortment of files and other hand and power tools.

The antenna body itself is 6 inches in diameter, so in order to mount the Nylon® blank for turning, I would have to cut it close. I learned that Nylon® cuts like the Tar Baby. It strongly tends to melt and wrap itself all up in the cutting tool and then it takes forever to get the tool back out of the work again. I gently triggered the saw until the blade just barely ran and sprayed coolant on the work and the blade every minute or so. Twenty minutes seems like forever to cut a six-inch circle when you’re used to working wood.

Turning Nylon® on the lathe creates bird’s nests of fishing line which will wrap everything that should rotate with everything that shouldn’t. I spent most of the time with the lathe turned off, pulling off scrap before it could foul up the work.

Two prototype bodies took as many days, but when assembled and tested the results looked encouraging. Now I had to build the feed networks. I’ve hand-cut microstrip many times before (maybe I should post instructions?) but have always had a milling machine to build the housings. Having no milling machine I had to fall back on the Palmgren, the Dremel and files.

Starting with a piece of half-inch brass rod, I was able to hack out one housing in six hours. Six hours working on a piece of brass a half-inch in diameter and an inch-and-a-half long. Six hours in the garage in June in Houston. Six hours of wondering, as the Dremel cooled off, whether I was going to finish the piece or slip and ruin it, or hurt myself, or burn out the tool. I made it after six hours.

I needed another housing, but decided to wait until Monday. Why put in all that work unless I knew the first third prototype would fly? That, and a recent acquaintance was coming over Friday afternoon to show me his Four Wheel Camper and talk about couch design. We messed around in the driveway, fixed a few minor things in his camper and talked about how to build a camper couch. Six O’clock rolled around and I had to go. Rob (my new friend) asked about the brass housing I showed him. Seems he had another friend with a machine shop and Rob was trained as a machinist. I cut him off a hunk of brass and wrapped it in the print.

Rob asked, “When do you need this?”

“Monday or Tuesday,” I answered thoughtlessly but truthfully. I figured to wait until Monday and then start hacking out the other one myself. I knew Rob was going away for the weekend.

Saturday was a pretty good day for me. I got the prototype finished (sample 03) and it tuned right up. All I had to do was spread the coils. Maybe I wasn’t so crazy? It was almost six O’clock and I decided to knock off for the day. I wanted to go out and work in the yard. The phone rang and it was Rob.

Rob: How’s it going?

me (feeling pretty good about what I had struggled to make): Well, I got a 29 MHz BW @ 1.5:1 VSWR.

Rob: What’s your gate code?

This guy I just met pulls into my driveway, rolls down his window and says, “Here. I gotta go; my wife’s p!ss3d…”

He dropped five little brass housings into my palm. Five little brass housings that would have cost me almost a week to build, but did in fact cost Rob (and Mrs. Rob) his Saturday off.

I walked into the house and after a while looked at the housings lined up on the counter. I felt like I had been touched by an angel.


So, no, I guess I’m not a self made man. I do what I can, knowing it’s not enough, knowing the world wants to cut me, bruise me, see me sweat, smell my fear, taste my tears, cause me to fail, …

… but I have some pretty good friends, you know?

Thanks, Rob, may God bless you.

Crying in the Wilderness

So they said to him, “Who are you? We need an answer! What do you have to say for yourself?”

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