Yagi-Uda Antenna for LoRa / LoRaWAN / Meshtastic @ 868MHz for 1.5mm² wire
A simple Yagi-Uda antenna designed for standard 1.5 mm² electrical copper conductors (~1.35 mm diameter), as commonly used in household electrical installations.
Large gap for easily inserting wires with soldered-on antenna cable
Driver Wire Holders (green/red)
No in-place soldering required!
Wire holder pieces and boom cutout allow easy installation of driver wires with the antenna cable already soldered-on!
Glued in-place
Wire Measuring Tool
Simply align put your copper wires with the measuring tool and use flush-cutters to cut them to precise lenghts
Vertical markings help align wire ends perfectly to the boom center
Optional Parts:
Clip-on tripod holder — fits standard camera mounts
Clip-on sights — for easy antenna alignment
7× hole diameter test pieces — to find the best wire fit (for experts)
TOOLS NEEDED
Wire-cutters
Multimeter
Drill and strong pliers
1.5 m of 1.5 mm² copper wire (~1.35 mm diameter)
Cyanoacrylate-based superglue (+ baking soda for extra strength)
HOW-TO / ASSEMBLY GUIDE
Print
Antenna Boom
Wire Cutting Tool
Driver Wire Holders (red/green parts)
There are multiple holder sizes—print them all to find the best fit.
Prepare the Wires
Pre-Cut, straighten, strip
Roughly cut wires to 180–200 mm.
Mount each wire into drill, run down pliers from the base to the top and slowly spin the drill → This removes the sheath and straightens the wire
Cut the wires
Cut the wires to the exact required lengths, use the wire measuring tool for this.
Use a flush cutter for precise results.
Note: The driver element requires two 80 mm wire pieces.
Make a sharpie-mark on the driver wire pieces (80mm)
Put the two driver wires into the measuring tool and make a pencil/shary mark on the wire where the vertical line is one the tool. Only apply solder on the shorter, right-hand-side, end of mark!
Soldering Time!
Strip and splice your antenna cable carefully, to expose both the inner core cable (signal) and outer shielding (ground) wires.
Solder one driver wire to the inner antenna core cable, the other to the outer shield cables.
Note: Avoid getting solder beyond the sharpy-marking we just made on the wire, otherwise the wire will not fit back into the driver holder piece anymore!
Solder the other antenna cable end to the other drive wire
Important Tips:
Don’t let solder go beyond your sharpie mark — or it will not fit into the holder anymore!
Avoid overheating the antenna cable! Melted insulation can short the core and shield.
Coat the driver wire with solder first and heat it up good. Then press the antenna cable into the molten solder and briefly heat it up as well. Apply a bit more solder if needed.
Curling the antenna cable ends around the driver wire to make free-hand soldering a bit easier!
Quality Control
During soldering, a couple things can go wrong, which may not be immediately noticeable:
Too much heat melts the inner plastic of the antenna cable => short between shield and core
Not enough heat was applied, causing a “cold” solder joint => only mechanical connection, but no electrical one
Use a multimeter in “beeping mode” to verify:
✅ Connection between antenna plug outer terminal ↔ one driver wire
✅ Connection between antenna plug inner terminal ↔ the other driver wire
❌ No connection between the two driver wires
❌ No connection between the inner/outer plug terminals
Final Assembly / Glueing
Driver Wires
Carefully slide the driver wires with the soldered-on antenna cable into boom cutout.
Don't break the thin antenna cables! The antenna cable terminal-end should come out of the top of the boom (not the side!).
Slide the driver holders onto the wires again
Use the wire cutting tool to measure how much the driver wires should stick out of the boom (vertical marks)
Use the pointy end of the tool (3mm) to verify they are not too much apart (best 3mm, at most 4mm!)
Use superglue (acytelate-based glue works best!) to glue the driver holders to the boom and to fixate the wires onto the holders
Optional reinforcement: Glue the antenna cable in place as well. For this, put the cable flat on the top of the boom and put a small "ant hill” of baking soda on top of it, close to the cutout hole. Then soak the baking soda with glue for hardening. This way the cable cannot wiggle on the solder joints anymore and there's not risk of them loosening over time.
Other wires
Stick the other wires into the dedicated holes of the antenna boom See below for correct order of the wires along the boom!
Use the wire measuring tool to align them perfectly centered The vertical mark on the tool denotes the distance between the wire-end and where it enters the boom. → Measure on BOTH sides! If there's always one side off, check if you're using the right wire!
Put a drop of glue on each side where the wire touches the boom. You can also apply a bit of baking soda here for more strenght.
Do a final quality control check:
Measure connections again with the multimeter in "beeping-mode"
Measure with the tool again whether all wires are centered and driver gap is correct
Done! You have a great Yago-Uda antenna for your LoRa node now!
→ Please share fotos and test results! ←
BOOM WIRE ORDER
The wires go into the boom in this order:
Element
Length
Notes
Reflector
169 mm
Driver / Dipole
2× 80 mm wires, 3 mm gap (≈ 163 mm total)
Boom cutout
Director D1
153 mm
Director D2
152 mm
Director D3
150 mm
Note about 3d-printing small holes
3D Printing Small Holes
The wire holes (~1.35 mm) are very small — similar to nozzle diameters (0.2–0.4 mm), so slicers may round dimensions slightly, causing inaccuracies and too large/small holes. The provided .3MF file was tested with a Bambu Lab A1 using PLA, but fit may vary. If the wires are too tight or loose, you can adjust the hole diameters in TinkerCAD: https://www.tinkercad.com/things/5KASKHN3Dbb-yagi-uda-lora-antenna-for-868mhz-135mm-wire
Click on the model whose holes you want to modify, then click “Un-group”
Do this a couple times until you are down to the part-level, where you see the negative part for the hole:
Zoom in, click on the hole, and then on the white squares to resize it (enter by hand rather than dragging!)
Now the hole is actually a bit off center! We need to align it again with it's outer shape, both horizontally and vertically. For this, click on the hole first, then shift-click on the outer piece, then click on the alignment button. Finally, click on the circled dots to align. (Watch out not to move the wrong part!)
Now we need to group the objects again. Drag your mouse over the canvas (so it draws a selection-rectangle) and select all parts of the model. Then click on the “merge-group” button:
Finally, select the model again and click Export → STL
If you need other frequencies / wire sizes, feel to modify the TinkerCAD of this model and publish a remix (attribution required)!
Javascript Version 2025-10-03 by 3G-Aerial, based on DL6WU.BAS source code Long-yagi DL6WU ------------------------------------------------------------- Driven element (dipole) form: Straight Element shape: Round ------------------------------------------------------------- Frequency f: 868 MHz Wavelength λ: 345 mm Element diameter d: 1.35 mm Boom side D: 20 mm
Total number of elements: 5 Boom length: 232 mm Gain: 10 dBi (approx.) ------------------------------------------------------------- Reflector length R: 169 mm Reflector position R = 0 ------------------------------------------------------------- Dipole length F: 163 mm Dipole position F (R-F): 69.1 mm Gap at connection point g <= 4.6 mm ------------------------------------------------------------- Length D1: 153 mm Director position D1 (R-D1): 95 mm Distance F-D1: 25.9 mm ------------------------------------------------------------- Length D2: 152 mm Director position D2 (R-D2): 157 mm Distance D1-D2: 62.2 mm ------------------------------------------------------------- Length D3: 150 mm Director position D3 (R-D3): 231 mm Distance D2-D3: 74.3 mm ------------------------------------------------------------- Elements on a dielectric boom. Boom-correction is not taken into account.
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