Whip Antenna Calculator - OneSDR

This post includes a Whip Antenna Length Calculator and provides background information on their definition and practical applications.

Calculator

The physical length of the whip antenna depends on frequency of operation.

Enter

Frequency with the appropriate units (kHz, MHz, etc.)
Length as a function of wavelength (The most common is the quarter-wave whip, which is approximately  λ/4 in length)

The tool will provide the physical length of the antenna (select the units cm, inch, etc. using the drop down menu)

Example Calculation

At 5800 MHz, the length of a quarter wave whip antenna is 1.29 cm.
At 2450 MHz, the length of a λ/4 whip is 3.06 cm.

As the frequency of operation decreases the length of the antenna increases.

Background

What is a whip antenna?

A whip antenna is a type of antenna consisting of a straight flexible wire or rod that can be either base-loaded or center-loaded. The most common form is the quarter-wave whip, which is approximately one-quarter of a wavelength long at the frequency of operation.

These antennas are typically used for terrestrial and marine applications in the VHF (Very High Frequency) and UHF (Ultra High Frequency) bands. The picture below shows an example – they’re more common than you might think.

Key Characteristics of Whip Antennas:

Flexible Design: Whip antennas are often made flexible so they can withstand wind and movement without breaking. This flexibility is achieved through the use of materials like spring steel or fiberglass.
Mounting: They can be mounted on vehicles (such as cars, boats, and aircraft) for mobile communication, as well as on portable devices like walkie-talkies and handheld radios. Fixed whip antennas are also used in base station applications.
Omni-directional Pattern: Whip antennas typically exhibit an omni directional radiation pattern, meaning they radiate or receive signals with relatively equal strength in all horizontal directions, making them ideal for mobile communication where the direction of the signal source or destination can vary.
Efficiency and Bandwidth: The efficiency and bandwidth of a whip antenna depend on its length and the specific design. A quarter-wave whip offers a good compromise between size and performance, providing reasonable bandwidth and efficiency for many applications.
Loading Coils: To make them physically shorter than a quarter wavelength and still perform effectively, whip antennas may include loading coils. These coils add inductance to compensate for the reduced length, allowing the antenna to resonate at its intended frequency. The picture below shows an example of this

Applications:

Mobile Communications: Widely used in vehicle communications systems, including police, fire, ambulance, and taxi radios, as well as personal vehicles for amateur radio and CB (Citizens Band) radio.
Portable Devices: Common in handheld transceivers and portable radio systems, where their compact and durable design is advantageous.
Remote Control Systems: Used in remote control transmitters for cars, drones, and other RC devices.
Wireless Networking: Some wireless networking devices and routers use whip antennas for Wi-Fi or other types of wireless connections, though designs may vary with application-specific requirements.

What is the gain of a whip antenna?

Antenna gain of 2 dBi typical for a whip with a ground plane of λ/2. Use the antenna gain and frequency of operation to determine the range of a wireless system.