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From the Field: Electrical Engineering as a Hobby

We get by with a little help from our friends, specifically Adam Carlson.

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Hello, my name is Adam Carlson and I am addicted to learning.

No really, I am, and that is the fun part! Because of my addictions to learning and creating things, engineering and design were a natural fit. If you couple this with a love of aviation, you get an aerospace engineer. Today, I work for GE Aviation designing jet engines, though because I love learning, I did not stop with aerospace engineering. In my free time, I have taken up learning other branches of engineering. I had, for many years, an interest in electronics. Back in about 2010, I was tired of people telling me that what I wanted to do in electronics was not hard, they just did not have time to help me. I asked myself, “How hard can it be?” (Yes, I know that this is a dangerous state of mind when coupled with a desire to learn.) So I set out to learn electrical engineering.

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What in the world inspired this desire to learn electrical engineering, you might ask? Well in a few short words: RC submarines. You are probably wondering if I am just trying to pull one over on you, or if they come with working torpedoes. Yes, RC submarines are a real thing; yes, we do have submarine races (it is not just a euphemism); and yes, some can fire torpedoes. As I got more involved with the hobby, the more I saw the wonderful, mechanical claptrap that was used to control many of the systems in the boats. These systems, though, were often unreliable due to their mechanical nature and operation in hot and humid environments. I could see that these systems could easily be simplified and improved upon with the addition of electronics.

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It was at this time that I came across SparkFun. It can be hard when you are trying to learn electronics from scratch. At the time, there were not a lot of resources that were easily available. Arduino was really just beginning getting legs, and had not yet achieved the recognition it has today. SparkFun, with its forum, was a great source of learning. Things like, do I use a linear or switching regulator? Where can I get a box of assorted components without having to pay a large sum of money and get 100 of everything?

These things may seem like simple questions to most, but to me at the time, they were not simple. Since then, I have progressed substantially, including becoming the editor of Electroschematics.com. I am currently designing a radio receiver (yes, this has been a very long project) for RC submarines. In the process I picked up a LimeSDR. These are fantastic devices at a really great price point. They have many advantages, including covering a very large bandwidth of signal spectrum. The downside is that it really is just a bare board without the nice finishings of a case. For my application, I plan to use this as a poor man’s VNA. To do this, I need to get a few u.fl to SMA cables, and a few bare SMA connectors to make a standards set (I plan to follow this link as a reference). The case will be 3D printed and lined with metallic tape to give the enclosure shielding properties.

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Why go to all this length to get a VNA up and running? Well, for starters, I had a few hundred dollars that I could spare, but not a few thousand dollars to get a “real” VNA. Second, I am addicted to learning. Third, and this is the actual technical reason, submerged antennas not only are too long once submerged, but they go through a change in impedance. There are very few papers out there that will help calculate this. There is software that could be used, but once again, this type of software tends to be tens of thousands of dollars for a license, and that is hard to justify on a hobby budget. So instead, we will go back to old method of using basic principles to get close to a design solution, then use testing to refine that solution. I will let you know what I come up with once I am done.

Comments 15 comments

  • The photo of an SMA connector shows 4 each 1k resistors, i.e. a 250 Ohm load. Yet the referenced web page for making Vector Network Analyzer standards shows an SMA connector with two 100 Ohm resistors, i.e. 50 Ohms. So is the 250 Ohm unit some kind of known 5:1 VSWR standard?

    • I suppose it all depends on if you read it 102 or 201. If you read it 201, then it comes out to 4/200 Ohm resistors in parallel, that then equals 50 Ohm load.


  • Good article but I might suggest that electrical engineering is something you to go to college for.. You don't play around and suddenly become an EE, not even close. Without the fundamentals you cannot really understand what is going on, never mind the math involved. For example, you can play around with Arduinos all you want but never know how a computer actually works (assuming you care). I would encourage those of high school age to consider applying to engineering school if you have the interest. However, I would advise that EE is one of the most difficult programs so not for the faint hearted and your classmate will appear to be geniuses (At least I thought so). I would also second the comment concerning ham radio especially since you have to study to pass the exams especially at the higher license levels.

    • Don’t be fooled into thinking a formal degree is the only way to understand something. Someone who is passionate about learning something can learn everything and more than a formal student. The best reason for the degree is for your resume. I started out with just a CAD degree and became designer doing the same thing as the engineers I worked with. I learned overtime that I needed that piece of paper to get the next job. It’s the best way for HR to determine that you are qualified, at least for now. With escalating school prices who knows what the next 50 years will bring.

      • Very true. With passion and a desire to learn, you can go very far. I have loved the freedom of being able to study diverse topics since I have left school. It has allowed me to be able to make connections across disciplines that would have been hard to find in a siloed approach.


    • It all depends on what one considers playing around and one considers learning. They are not mutually exclusive. I agree that one can take learning to various levels depending on their aptitude and desire to learn. Also note, that I am a degreed engineer, just in another branch of engineering. The overlap in the fundamentals is significant despite the application being different. As to my classmates appearing to be geniuses, well this why we went into engineering, to be surrounded with like minded people who were "different" :)

      As to playing around with Arduinos and not understanding how an actual computer works, I would contend that this may one of the the best way to get an understanding of what our computers evolved from. By studying these small microcontrollers one learns how memory is handled, how code is converted to machine instructions, and many other concepts are directly leveragable to a general CPU. In fact, Intel at one point in time had their Arduino board with chips that were x86 instruction set devices and had early Pentium level performance.

      I currently have a dev kit on my desktop that has a Cortex M7 in it, and as far as processing power is more powerful than our family's first personal computer (486DX2-66 with math co-processor). The cortex M7 part benchmarks at ~460 DMIPS vs about 45 DMPIS for the 486. It really is amazing what these microcontrollers can do now a days.


    • There is absolutely no reason you have to go to college to learn hobby-level electrical engineering. He's not building actual submarines, he's building toys.

      • It gave me a chuckle to read this. I appreciate the support, and yes, there is a difference between building a life critical device and a hobby device.


  • What's a VNA? Lots of acronyms and fluff in this piece. How can I get information on what he is doing?

    • a VNA is a Vector Network Analyzer (https://en.wikipedia.org/wiki/Network_analyzer_(electrical)). It is a very expensive piece of measurement gear if you have to purchase it.

    • I appreciate you question, though I do ask for some level of civility in asking questions. I and others are happy to answer questions.

      As was mentioned, a VNA is a Vector Network Analyzer. It is used measure the performance of various radio frequency (RF) related parts and connections. It essentially sends out a signal that is a frequency sweep, and then it also listens to see if there is a return of that signal. The magnitude and phase of the return of this signal corresponds to performance parameters of the device under test (DUT).

      What I am doing with the LimeSDR is an application that was originally envisioned as a sample application. Is it fully equivalent to a $10k device, absolutely not, but is it better than having no device at all, for sure it is. While there are performance trade-offs, it still yields useful information.


  • I would second the usefulness of ham radio in this endeavour. With the right license and equipment the HF/MF/LF bands are accessible, and could give you the ultra-long wave communications that are so useful in submarine communications. See some interesting links below.

    http://www.arrl.org/radio-amateurs-and-america-s-secret-submarine https://sites.google.com/site/somaliaamateurradio/somaliaphotos27

    • I appreciate the encouragement. In this case, as I am operating in very low conductivity water (read not salt or brackish water), VHF and UHF will work. There is a gentleman that has tested devices in the 433Mhz and 915MHz ranges. With modern, high sensitivity RFICs it was possible to get a fully functioning submarine using a 433MHz transceiver. Using 915Mhz, he was only able to achieve about 3' (roughly 1m) in depth. While this is useful, it is not as useful as is required to operate a boat safely.


  • The Amateur (Ham) Radio world can be a wonderful resource of info on various radio and RF (Radio Frequency) equipment, including stuff done on a shoestring budget. I'd suggest checking out the ARRL (American Radio Relay League -- the "national" Amateur Radio club in the U.S.)

    • I have indeed found this to be true. I live next to where the Hamvention is held each year. There are some fantastic people that are in the hobby.


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