Build a Directional Antenna
8d3.
Build a simple directional antenna for either of the two frequencies used in ARDF.
The Tape-Measure Yagi (2 Meters)
The most popular Scout-friendly ARDF antenna project is the tape-measure Yagi — a three-element directional antenna made from inexpensive steel tape measures and PVC pipe. It’s lightweight, collapsible, and effective.
Materials
- 3 steel tape measures (at least 40 inches each) — dollar store tape measures work fine
- 1 PVC pipe, 3/4" diameter, about 36" long (the boom)
- 3 PVC cross fittings or hose clamps to mount the tape-measure elements
- 1 BNC or SO-239 connector (to connect the coax cable)
- Short length of RG-58 coax cable with appropriate connector for your receiver
- Electrical tape, zip ties, or hose clamps
- A hacksaw for cutting PVC
Element Dimensions (for 146 MHz)
| Element | Length | Position on Boom |
|---|---|---|
| Reflector | 41.5 inches | 0 inches (back end) |
| Driven element | 35 inches (two halves, 17.5" each, with gap at center) | 12 inches from reflector |
| Director | 33 inches | 24 inches from reflector (12 inches from driven) |
Reflector
- Length
- 41.5 inches
- Position on Boom
- 0 inches (back end)
Driven element
- Length
- 35 inches (two halves, 17.5" each, with gap at center)
- Position on Boom
- 12 inches from reflector
Director
- Length
- 33 inches
- Position on Boom
- 24 inches from reflector (12 inches from driven)
Assembly Steps
- Cut three tape-measure strips to the lengths above. Round or tape the cut ends to prevent sharp edges.
- Mount each strip to the PVC boom at the positions listed, using cross fittings or hose clamps. Elements should be perpendicular to the boom.
- The driven element is split into two halves with a gap at the center. Connect the coax cable center conductor to one half and the shield to the other half.
- Attach the coax connector and run a short cable to your receiver.
- Test: Point the antenna at a known VHF signal source and verify that the signal is strongest when the director end points at the source.
🎬 Video: Tape Measure Yagi Beam Antenna - Ham Radio Q&A — KB9VBR Antennas — https://www.youtube.com/watch?v=BmHoQrDfw-0