Filament Spool 49:1 Un:Un for EFHW
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A compact and portable 49:1 impedance transformer for End-Fed Half-Wave antennas.
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Updated at source:
Model information
- Source
- Printables
- Category
- Electronics
- License
- Open Community License v1
A compact, partly 3D-printed enclosure for a 49:1 End-Fed Half-Wave (EFHW) transformer, built into an empty Prusament filament spool. The Un:Un is designed for portable and field HF operation, it can be mounted to any supporting structure with paracord. The transformer is designed for an RF output of 25 W. Scale components accordingly to your usage. The Un:Un has a connection point for a counterpoise, though it is not necessary for all setups.
Materials:
1x FT140 -43 ferrite toroid
1x Panel-mount BNC male insert
~1.5 m 0.6mm enamelled copper wire
1x 100 pF / 1 kV capacitor
12x M3 * 5-6 mm screws
12x M3 standard nuts
2x M4 * 20 mm screws
2x M4 washers
2x M4 standard nuts
2x M4 T-nuts
3x zip ties
~1m paracord
Assembly:
HF Kits has made a nice guide on assembling a 49:1 Un:Un and EFHW element here.
Toroid winding:
Print settings:
PLA+ at the minimum is recommended for outdoor use. Minimum 3 walls, 20% infill. Normally, no supports or adhesion is required. See individual part notes for inserting the M3 nuts.