Despite its name, the length should not be truly random. Values close to half-wave multiples can produce extreme impedance.
Antennas · F1SYH
Random Wire
A Random Wire is an end-fed wire whose length is selected to avoid difficult impedances on the intended bands.
HF
Portable
Accord nécessaire
Operating principle
Main characteristics
Typical gain
Variable
Impedance
Très variable
Polarization
Mixte
Difficulty
Facile à intermédiaire
Dimensions and design
Choose a published practical length compatible with the desired bands and tuner range.
Construction and tuning
Step 1
List the required bands.
Step 2
Choose a length avoiding half-wave multiples.
Step 3
Install a suitable transformer, often a non-resonant 9:1.
Step 4
Add a counterpoise.
Step 5
Install a choke before the station.
Advantages
- Very easy to deploy.
- Low cost.
- Suitable for portable use.
- Several possible bands.
Limitations
- Requires a tuner.
- Variable efficiency.
- Common-mode current is frequent.
- Length requires careful selection.
History and origin
Tuner-fed wires have been used since early portable radio. Random Wire mainly means a non-resonant antenna.
Safety
The transformer and free end may carry high RF voltage.