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Quarter Wave Antenna Length Formula:
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A VHF (Very High Frequency) Quarter Wave Antenna is a type of antenna that is one-quarter wavelength long at the operating frequency. It's commonly used in the 30-300 MHz VHF band for various communication applications including FM radio, television broadcasting, and two-way radio systems.
The calculator uses the quarter wave antenna formula:
Where:
Explanation: The quarter wavelength is calculated by dividing the speed of light by four times the frequency. This gives the optimal length for resonance at the desired frequency.
Details: Proper antenna length is crucial for optimal signal transmission and reception. A quarter wave antenna provides good impedance matching and radiation efficiency for VHF applications.
Tips: Enter the frequency in MHz within the VHF range (30-300 MHz). The calculator will provide the optimal quarter wave antenna length in meters.
Q1: Why quarter wave instead of half wave?
A: Quarter wave antennas are more compact and when used with a ground plane, provide similar performance to half-wave antennas with better form factor.
Q2: What is the typical impedance of a quarter wave antenna?
A: A quarter wave antenna typically has an impedance of around 36 ohms, which makes it easier to match to standard 50-ohm coaxial cable.
Q3: Do I need a ground plane for quarter wave antennas?
A: Yes, quarter wave antennas typically require a ground plane or counterpoise to function properly, as they are unbalanced antennas.
Q4: Can this calculator be used for other frequency bands?
A: While the formula works for any frequency, this calculator is specifically designed for the VHF band (30-300 MHz).
Q5: How accurate is the calculated length?
A: The calculation provides the theoretical length. Actual construction may require slight adjustments due to factors like antenna diameter and surrounding environment.