QRP 40M EFHW Reel Style Housing

thingiverse

**Latest version on my [Printables page](https://www.printables.com/model/398802-qrp-40m-efhw-reel-style-housing). Please consider downloading from there, as it helps me earn free filament.** # Overview This design combines the functionality of both a transformer housing and wire winder into a convenient package that is both easy to deploy and store. It is sized to hold an FT140-43 toroid and approximately 67ft of 18AWG wire, making it suitable for a QRP* 40M EFHW. *\*I'm not sure what kind of power the FT140-43 can take; I'm only ever putting up to 20W into it, and it seems to handle that without issue.* # Features - Circular shaped wire winder keeps wire bends smooth and even preventing sharp turns/bends found in some styles of wire winders. - Reel style allows for quick and easy deployment by attaching the end of the antenna to an anchor and walking away using a pen or stake through the center of the reel as an axle. - Holes around the outside of the housing provide choice of attachment points. - Two-part insulator works not only as a regular insulator, but also as a clip to hold the end of the wire to the housing. Shock cord between the two pieces provides the extra tension needed to ensure the wire is held securely and won't come out of place. # Parts List ## Printed Parts - reel-body.stl (x1) - reel-lid.stl (x1) - insulator.stl (x1) - insulator-clip.stl (x1) ## Purchased Parts *Links provided for convenience; feel free to purchase elsewhere.* - [FT140-43 Toroid (x1)](https://www.amazon.com/dp/B0178IABXW) - [Enameled Wire](https://www.amazon.com/dp/B07H7FQTZM) - [18 AWG Hookup Wire (~67ft)](https://www.amazon.com/dp/B07328N9PM) - [1KV 100pf Capacitor (x1)](https://www.amazon.com/dp/B08278W95D) - Adhesive - [this](https://www.amazon.com/dp/B001F7E9VI) works great; 2-part epoxy would be fine as well. - [3/16 Diameter Shock Cord (~10cm)](https://www.amazon.com/dp/B06WLGYS1F) - [Zip Ties (x2)](https://www.amazon.com/dp/B09N8LTYTV) - [BNC Bulkhead Connector (x1)](https://www.amazon.com/dp/B07DGV6482) # Assembly *Note: Wrapping the toroid and the theory involved with doing so is outside the scope of this guide. There are many good resources online for this information, and the only real requirement is not to cross the toroid with wire in such a way it won't fit into the housing.* **Some Resources:** - https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/ - https://www.hfkits.com/build-instruction-impedance-transformer-for-end-fed-antennas/ - https://vk3il.net/projects-antenna/efhw-matching-unit/ ### Printing Parts and Post Processing Print the parts in the orientation that provides the most contact with the build plate. The only part that you may want to use supports with is reel-body.stl, however, if your printer has decent bridging ability, you can probably skip it. There shouldn't be much post processing required, but I would recommend threading the lid onto and off of the body a couple times to smooth them out. ### Mounting Parts Once the parts are printed and the toroid is wrapped, mount the BNC connector in the appropriate hole in the body. Next, seat the wrapped toroid over the center post and use zip ties to secure it to the attachment points. With the toroid secured in place, make the appropriate solder connections between the enameled wire and BNC connector and add the capacitor. Next, decide what you want to use for strain relief. The element wire can be wrapped through one of the holes on the outer rim of the case, or one of the zip ties holding the toroid can be used (see picture). Once you've decided, route the wire appropriately and connect it to the appropriate spot on your transformer. ### Construct the Insulator Run the end of the element through one of the small holes in insulator.stl and back through the other small hole. Next, tie a knot in one end of the shock cord. Run the shock cord through the large hole in insulator.stl and the small hole in the middle of insulator-clip.stl and tie a knot in the other end of the shock cord to tie the two parts together (see pictures for more details). The two nubs in insulator-clip.stl can fit into the holes in the housing to allow the end of the element to be held in place. ### Tuning and Testing Once all the parts are mounted and the insulator attached, screw on the lid (if desired), set up the antenna and tune it with whatever method you prefer. **NOTE: this housing is designed to be glued together once complete. Without adhesive, the threads may shear off the center post if it's dropped. Be cautious with the housing during testing.** ### Completion Once you're satisfied with the tuning, remove the lid and fill the groove with adhesive. Screw on the lid until the BNC cutouts line up, then use clamps to hold the two pieces together until dried. Once everything has set, the element can be wrapped onto the housing with the insulator clipped on to secure everything in place.