November 20, 2025
Thanks to the modeling Bill, KB2SA has done on the value of using a square to round transition on the septum feed of small 23cm moonbounce dishes like his 1.9M dish, the 1.5M "Cooker" and the 2.4M W2HRO folding dish, I thought it might be something worth trying to improve my EME performance. The concept is that the transition will more evenly illuminate the whole dish for an increase in performance. Desire and reality came together when Ingebrigt, LB6B published a public use .step file so most 3D printers could knock out the 240mm x100mm transition. A search of local possibilities here in Bozeman, Montana for 3D printing turned up nothing very professional, responsive, or reasonably priced. Drat!
I turned to the Internet and found Craftcloud, a jobber that bids out 3D printing projects to several vendors finding the best price and printing options. After uploading LB6B's .step file and selecting PETG as my material, I immediately saw a reasonable price quote. Bingo! Credit card out, let's make it happen.
My job was sent to Detroit 3D Manufacturing and in a week a well boxed transition piece was at my door. Detroit 3D shipped direct. Total price including shipping $45.00. Bonus - if you're flush with cash you can get a 3D printed transition in aluminum for $160. Thank you, but I'll use a roll of copper foil tape from Amazon on the interior of my transition.
I installed the transition piece on my 1.5M "Cooker" dish today while the weather was still good, and ran some sun noise tests to find the new focus. After we get on the other side of new moon I'll be ready to run with the usual suspects and see what performance the square to round transition brings.
KB2SA's detailed paper on maximizing the performance of his 1.9M dish, including the concept of a square to round transition can be found here.
LB6B's very comprehensive article on 3D printing square to round transitions including the .step file is here.
Thanks also to Dave, KG0D who is always testing suggested improvements for our collection of small EME dishes and keeping meticulous records.
 |
| 3D printed 240mm x 100mm transition in PETG with copper foil tape applied. |
 |
| 3D printed transition (white piece) installed. Cables need to be moved a bit. |