Four wires form two successive V sections. Travelling waves combine toward the terminating resistor.
Antennas · F1SYH
Rhombic antenna
The Rhombic is a very large diamond-shaped antenna, normally resistively terminated for long-distance HF communication.
HF
Directive
Onde progressive
Operating principle
Main characteristics
Typical gain
Élevé selon longueur et hauteur
Impedance
Environ 600 à 800 Ω
Polarization
Principalement horizontale
Difficulty
Très avancée
Dimensions and design
Each side is commonly several wavelengths long. Diamond angles depend on frequency, height and desired take-off angle.
Construction and tuning
Step 1
Define the main azimuth.
Step 2
Calculate all four sides.
Step 3
Install four widely separated supports.
Step 4
Build a balanced feed system.
Step 5
Install a high-power terminating resistor.
Step 6
Check grounding and losses.
Advantages
- High gain.
- Relatively wide bandwidth.
- Strong directivity.
- High power capability.
Limitations
- Requires enormous land area.
- Single main direction when terminated.
- Power dissipated in the resistor.
- Four substantial towers.
History and origin
The Rhombic was widely used during the twentieth century for commercial, diplomatic and military long-distance links.
Safety
The terminating resistor may dissipate substantial power and requires protection against contact and fire.