As electrical length increases, the pattern develops several lobes at angles related to wire length.
Antennas · F1SYH
Long Wire
A Long Wire is a conductor generally longer than one wavelength at the operating frequency.
HF
Fil long
Directive selon longueur
Operating principle
Main characteristics
Typical gain
Variable, parfois directionnel
Impedance
Élevée et complexe
Polarization
Mixte
Difficulty
Intermédiaire
Dimensions and design
There is no universal length. Geometry should be selected according to band and desired directions.
Construction and tuning
Step 1
Define the main bands.
Step 2
Study expected lobe directions.
Step 3
Install a suitable transformer.
Step 4
Provide a real RF return path.
Step 5
Add a feed-line choke.
Advantages
- Simple mechanical construction.
- Possible gain on selected bands.
- Several usable bands.
- Suitable for large properties.
Limitations
- Pattern is hard to predict without simulation.
- Highly variable impedance.
- Common-mode current.
- Large required space.
History and origin
Long wire antennas were used early for long-distance communication and directional arrays.
Safety
An end-fed Long Wire often carries high RF voltage.