The resistor absorbs part of the energy that would otherwise be reflected. SWR remains moderate over a wide range, but energy is dissipated as heat.
Antennas · F1SYH
T2FD
The T2FD is a tilted folded dipole terminated with a non-inductive resistor. It favours bandwidth over maximum efficiency.
HF
Large bande
Résistance terminale
Operating principle
Main characteristics
Typical gain
Inférieur au dipôle résonant
Impedance
Large bande avec transformateur
Polarization
Selon installation
Difficulty
Avancée
Dimensions and design
Length depends on the desired lowest frequency. Resistor and transformer must be rated for impedance and transmitter power.
Construction and tuning
Step 1
Define the lowest frequency.
Step 2
Build the parallel conductors.
Step 3
Install a non-inductive resistor.
Step 4
Add a broadband transformer.
Step 5
Check heating at intended power.
Advantages
- Wide bandwidth.
- Relatively stable SWR.
- Stable reception.
- No retuning on every band.
Limitations
- Less efficient than a resonant antenna.
- Power dissipated in the resistor.
- Expensive power resistor.
- Large size on lower bands.
History and origin
The T2FD was developed for military and professional communications requiring wide frequency coverage.
Safety
The terminating resistor may become very hot during transmission.