The personal website of Scott W Harden

Scott is now Licensed! (KJ4LDF)

I've taken the plunge into the geek world by becoming a licensed amateur radio operator. My wife and I both took our technician exam last week, and this morning I discovered that our call signs have been processed. I'm KJ4LDF, she's KJ4LDG. I'm a little disappointed that my call sign has an "F" in it. On the air, "F" and "S" sound similar, so I'm more likely to have people asking me to repeat it. The phonetics are Kilo, Juliet, Four, Lima, Delta, Foxtrot. Foxtrot! How silly is that? [sighs] Either way, I'm glad I've been added to the database, and am now legally able to begin broadcasting on VHF/UHF.

Beacon stuff (like I wrote about in the last post) would best involve lower frequencies, which would mean I have to take another exam to get a higher license class.

This article's source was last edited on September 10, 2020.
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Pointless Beacon Idea

I got an idea today for an odd but interesting project. The idea is still in the earliest stages of development, and I further research the idea (for example, I don't even know if it's legal) but it's a cool idea and I want to try it. I know I'll learn a lot from the project, and that's what's important, right? So, here's the idea: I want to build an incredibly simple, low power radio transmitter that broadcasts data on a fixed frequency. Data is provided by a microcontroller. What data will it transmit? uh... err... um... okay it doesn't really matter and I don't even know, I just want to do this project! Maybe temperature and light intensity or something. Who cares - it'd be fun to make regardless of what it transmits. I could put it all into a drybox (pictured).

Once properly closed, this box will keep everything in pristine working condition by protecting against rain, heat, snow (not that we get much of that in Orlando), hurricanes, and perhaps even Florida panthers and bears (oh my). I'd like to make a glass (or plexiglas) window on the top so that light could get in, hitting solar panels, which trickle-charges the battery housed in the device as well.

My idea is to keep construction costs to a minimum because I'm throwing this away as soon as I make it. My goal is to make it work so I can toss it in some random location and see how long it will run. Days? Weeks? Months? Years? How cool would it be to go to dental school, come back ~5 years from now, and have that transmitter still transmitting data. I've been poking around and I found someone who did something similar. They built a 40mW 10m picaxe-powered beacon using a canned oscillator as the transmit element.

I understand the basics of radio, amplitude and frequency modulation (AM and FM), etc., but I've never actually built anything that transmits radio waves. I could build a SoftRock radio, but my educational grounding is in molecular biology. I know little about circuit-level electronics, electrical engineering, and radio theory... so my plan is to start small. This project is small enough to attack and understand, with a fun enough end result to motivate me throughout the process.

This article's source was last edited on September 10, 2020.
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Is Google Re-Indexing My Life?

After several years of persistent writing on this website I was forced (by my undergraduate university's difficult course loads) to stop adding to this blog - something I consider to be one of the most significant projects I've ever worked on, with brain-to-text recordings of my thoughts spanning almost a decade of time. After a few years of suspended writing, Google went from loving me (sending me thousands of page views daily) to forgetting about me (nothing. silence. nada.). Now that my thesis requirements have been completed, I'm trying to re-energize my writing in an attempt to document the projects I work on which, without this website, would likely be forever forgotten even by me. It appears that the burst of new writing has regained Google's attention. Google for terms such as "data smoothing in python" and it favors my site. Google is slowly, but surely, re-indexing my pages and assigning them values of relevance which are approaching (but still a tiny fraction of) what they were before my hiatus. Here's a chart from google's analytics demonstrating an estimation of IP visits per day (visitors) and their locations.

This article's source was last edited on September 12, 2020.
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⚠️ Warning: This article is obsolete.
Articles typically receive this designation when the technology they describe is no longer relevant, code provided is later deemed to be of poor quality, or the topics discussed are better presented in future articles. Articles like this are retained for the sake of preservation, but their content should be critically assessed.

Post-Defense Day 1

Two hours after getting home from work I'm already basking in the newfound carefreeness thanks to the successful completion of my thesis defense (and graduation requirements). Yesterday I went to SkyCraft, early this morning I posted a schematic diagram of a basic circuit concept for a radio/microphone interface box with tone generating functions, and this afternoon I finished its assembly. It's hacked together, I know, but it's just a prototype. What does it do? It's complicated. It's basically just an exercise in microchip programming.

Future Scott reacts to this in August, 2019 (10 years later)

LOL! That's a pipette box! A chip socket was sunk into a plastic enclosure somehow! And that "regulated power supply" is an LM7805 on non-metallic perfboard screwed to two Jenga blocks!

Here's the little setup with the main control unit and a DC to DC regulated power supply / serial microchip programmer I made.

Here's the main control box. Notice the "2-way lighted switches" which I described in the previous entry. I found that proper grounding (floating pin prevention) was critical to their proper function. I'm still new to these chips, so I'm learning, but I'm making progress!

Getting a little artsy with my photographs now... this is the core of the device. It's a picaxe 14m!

This is a 5v regulated power supply I built. The headphone adapter is for easy connection to the serial port. It has a power switch and a program/run switch (allowing use of pin 13, serial out) while still "connected" to the PC.

I've slightly improved the connection between my radio's coax cable to the J-pole antenna I made.

I'm able to get pretty good signals from this antenna, but it's probably not likely to do much to my assembly skills (and lack of tuning), and more likely due to the fact that I have an unobstructed view of middle/southern Orlando from the 3rd story of my apartment balcony. I could probably wire up a rubber duck on a stick and get good results with that location! I'll miss my reception when I move.

This article's source was last edited on September 10, 2020.
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Transmitting Around the World

One of my recent fascinations is QRSS, a super-low power mode of transmission over the airwaves. Picture this: get a ham radio setup which outputs dozens of watts of power, use a microcontroller to transmit data (frequency-shifting Morse code), use FFT on the receive end to view it on the computer, now increase the time between the "beeps" to tens of seconds and decrease the power to milliwatts and receive the signal thousands of miles away - that's QRSS! How cool! I want to try this badly... but I have to get back to lab - I have a thesis to write!

This article's source was last edited on September 10, 2020.
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