For four years in the mid-1990’s, I worked for a county-wide ambulance company in rural western Pennsylvania. For radio communication, we used the Motorola HT-600 portable radio’s – affectionately referred to as ‘bricks’; they were roughly the same size, weight, and durability as a construction brick.
During my time in graduate school, I started to feel a bit nostalgic and saw a Motorola HT-600 for sale on eBay for a reasonable price. I quickly purchased it, and had it on my desk the next week. A month went by, and I was starting to realize that what I had done was to purchase an expensive paperweight. In talking with some friends, I became aware of Amateur Radio (aka ham radio) and the possibility of having my Motorola HT-600 reprogrammed to the local Amateur Radio repeater frequency. During the summer of 2000, I passed the FCC licencing exam to become a licenced Amateur Radio Operator – Technician class.
Since then, my interest in ham radio has only grown. In the last few years, my interest has revolved around constructing antennas to better receive signals from further distances.
My latest project involved building a di-pole antenna based on materials readily found at a hardware store (electrical conduit box, 5/16th threaded rod, assorted nuts and washers, …). The first itteration worked, but it was a bit flimsy and didn’t look great. To seal the conduit box, I was only able to find rounded capped ends – not great for drilling a hole to pass a threaded rod through.
The area for improvement was in how the antenna elements (the threaded rods) were held inside the conduit box. For the second iteration, instead of working with a ‘cap’ that fit over the 1″ diameter circular opening at the top and bottom of the conduit box, I decided to build an insert that had a 5/16th hole already molded into it. Enter the 3D printer and rapid prototyping.
In one afternoon, I was able to take some measurements of the electrical conduit box, and design a part with the web-based 3D design software TinkerCad. The first part was printed in a few hours , and the dry-fitting later that day revealed that a design modification was needed. The next day I was able to modify the original design, and print a second version. This version fit perfectly! The only catch was that it was printed with Polylactic acid filament (PLA). PLA is commonly used in 3D printers, and has a lot of good qualities. Unfortunately, one of the drawbacks of PLA is that it has a relatively low melting point (if you were around in the 1980’s, think of the melted glob that resulted from leaving crayons in a car on a summer day).
The next step was to visit the 3D Hubs website and find someone who would be able to print the part I designed in a sturdier material such as ABS, which doesn’t start to droop / melt until temperatures reach 105° celcius. I was able to quickly identify a number of options for having my part printed in ABS. I decided to go with a company called Leap 3D LLC out of New York City. Within three days of sending them my final design file, I received the parts via USPS.
Assemblig the antenna took about half an hour, and the results looked much cleaner than what I had originally put together with what I could find at the hardware store. The photo below shows what the center portion of the antenna now looks like. The white horizontal pipe is mounted to a vertical pole such that the antenna is free-standing.
3D Printing allowed me to improve upon an existing idea that I had. I was able to go through some design itterations and send the final design out for printing within a few days.
The tutorials on the TinkerCad YouTube channel were a great resource as I was learning the software as I was building my first 3D model.