Antenna Tuner Project Box and Knob

thingiverse

This project is offered as an alternative to several components supplied in the "Manual Days" inexpensive antenna tuner (ATU) commonly available from the usual sources for <$20. This project includes: - knobs designed to fit over the tablet-shaped portion of the polyvaricon capacitor shaft (the turny part) and tune without slipping or having to rely on a toothed washer to provide friction. The knob is sized to allow use of the screws provided with the radio and has a hole in the top to accommodate the cap of the original knob. It also has a nifty pointer. - a project box that includes holes to secure the polyvaricon capacitors with screw holes that will allow use of the original screws without risk of damaging the capacitor plates. There are also holes to allow the custom knobs to fit the capacitors, holes for the shaft and registration lug of the 12-position switch, a hole for the 2 position tuning switch, a hole for the tuning LED, and holes to accommodate BNC connectors. - a lid to keep the bugs out and the parts in. It's sized to fit M3 flat-headed screws around 8 mm in length. You'll need to come up with a new label for the ATU as I've relocated the tuning LED so you can actually see it while tuning. The capacitors have been moved slightly as well. If someone wants to design a new label, I'll be happy to include a pdf of it in this repository. If you embark on this project, do NOT rely on the instructions or schematics provided (or more likely not provided but found online). The transformer is shown backwards on the PCB and the switch wiring is described incorrectly. Sverre Holm's (LA3ZA) site at https://la3za.blogspot.com/2022/06/reversing-inductor-on-chinese-qrp.html describes the inductor wiring and includes a link to a video from Carol (KP4MD). Pay attention to both. Carol's video also shows some performance testing data. The results from such an inexpensive ATU are quite acceptable. Bob (VK1ERF), has a pretty extensive resource on the ATU at https://digitalshack.org/qrp-1-30mhz-antenna-tuner/. He is still making changes to the document so it may not include the changes mentioned above. Be sure to pay particular attention to Carol and Sverre's inductor info.