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End Fed Half Wave Antenna Length Formula:
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An End Fed Half Wave (EFHW) antenna is a type of wire antenna that is fed at one end rather than the center. It offers a convenient and efficient antenna solution, particularly for portable and limited-space operations.
The calculator uses the formula:
Where:
Explanation: This formula calculates the physical length of a half-wave antenna for a given frequency, which is optimal for efficient radiation and reception.
Details: Proper antenna length is critical for optimal performance, impedance matching, and efficient power transfer between the transmitter/receiver and the antenna.
Tips: Enter the desired operating frequency in Hz. The calculator will determine the optimal half-wave length for your end-fed antenna.
Q1: Why is a half-wave length important for antennas?
A: Half-wave antennas offer a good balance between size and performance, with predictable radiation patterns and impedance characteristics.
Q2: Does this calculation account for velocity factor?
A: No, this calculation assumes free-space propagation. For practical antennas, you may need to apply a velocity factor (typically 0.95-0.97 for wire antennas).
Q3: Can I use this for other antenna types?
A: While the formula is general, this calculator is specifically designed for end-fed half-wave antennas which have different impedance characteristics than center-fed antennas.
Q4: What frequency ranges work best with EFHW antennas?
A: EFHW antennas work well across most HF bands and can be designed as multiband antennas with appropriate matching networks.
Q5: Do I need a matching unit with an EFHW antenna?
A: Yes, end-fed antennas typically require an impedance matching unit (unun) to transform the high impedance at the end feed point to the standard 50-ohm impedance of most radios.