The Cubical Quad Antenna Calculator helps you quickly estimate the basic dimensions of a 2-element or 3-element Cubical Quad antenna from its operating frequency and velocity factor. Instead of calculating wavelength, loop perimeters, side lengths, and element spacing manually, you can enter a few values and get the main design dimensions in meters.

The calculator accepts three inputs: frequency in MHz, number of elements, and velocity factor. For a 2-element design, it calculates the driven element and reflector. For a 3-element design, it also calculates the director. It also provides an estimated gain based on the selected element count.

The calculator uses a simplified wavelength-based model. Its formulas set the driven-element perimeter to one wavelength, the reflector perimeter to 1.05 wavelengths, and the director perimeter to 0.95 wavelengths. Recommended element spacing is calculated as 0.15 wavelength.

What does a Cubical Quad Antenna Calculator calculate?
It calculates the wavelength, driven-element dimensions, reflector dimensions, director dimensions for a 3-element design, recommended element spacing, and an estimated gain.

These values are useful as initial design dimensions. The final performance and dimensions of a physical antenna can vary because of construction details, conductor characteristics, feed arrangements, surrounding objects, installation height, and tuning.

What Is a Cubical Quad Antenna?

A Cubical Quad antenna is a directional antenna that uses loop-shaped elements rather than the straight elements commonly associated with a Yagi antenna. The loops are typically supported using spreaders and a structural framework.

A basic Cubical Quad design can contain two or more elements. In this calculator, the available configurations are specifically 2-element and 3-element designs.

The three main element types used in the calculator are the driven element, reflector, and director.

Driven Element

The driven element is the primary radiating element and is connected to the feed system. In the calculator's model, its total loop perimeter is set to one calculated wavelength.

Because the calculator assumes a four-sided loop with equal sides, the side length is calculated by dividing the perimeter by four.

Reflector

The reflector is placed behind the driven element and is modeled as slightly larger than the driven loop.

The calculator uses:

Reflector perimeter = 1.05 × wavelength

Its side length is then calculated by dividing the perimeter by four.

Director

The director is used in the calculator's 3-element configuration. It is modeled as slightly smaller than the driven element.

The calculator uses:

Director perimeter = 0.95 × wavelength

The director side length is one quarter of its calculated perimeter.

Adding a director makes the design more complex than the 2-element version, but the calculator also provides a higher nominal gain estimate for the 3-element configuration.

How the Cubical Quad Antenna Calculator Works

The calculator follows a straightforward calculation process.

Step 1: Enter the Frequency

Enter the desired operating frequency in MHz.

For example:

144 MHz

Frequency is the most important input because wavelength is directly determined by frequency. As frequency increases, wavelength decreases. As frequency decreases, wavelength increases.

Step 2: Select the Number of Elements

Choose either:

• 2 elements
• 3 elements

A 2-element design consists of a driven element and reflector.

A 3-element design consists of:

• Reflector
• Driven element
• Director

When you select three elements, the calculator adds the director perimeter and director side length to the results.

Step 3: Enter the Velocity Factor

The calculator accepts a velocity factor between 0.8 and 1.0.

The selected velocity factor is applied directly to the calculated free-space wavelength.

Step 4: Calculate the Wavelength

The calculator uses:

λ = (300 / f) × VF

where:

• λ = calculated wavelength in meters
• f = frequency in MHz
• VF = velocity factor

Step 5: Calculate the Loop Dimensions

Once the wavelength is calculated, the calculator determines the perimeter of each loop.

For the driven element:

Driven perimeter = λ

The four equal sides are then calculated as:

Driven side = driven perimeter / 4

The same approach is used for the reflector and director.

Step 6: Calculate Element Spacing

The calculator recommends:

Spacing = 0.15 × λ

This gives the user a wavelength-based starting point for positioning the antenna elements.

Cubical Quad Antenna Calculator Inputs Explained

1. Frequency

The Frequency input specifies the operating frequency for which the Cubical Quad is being designed.

The calculator expects the value in MHz.

For example, you could enter:

• 7 MHz
• 14 MHz
• 28 MHz
• 50 MHz
• 144 MHz

The frequency determines the wavelength and therefore affects every calculated physical dimension.

A higher frequency produces a shorter calculated wavelength. This means the resulting loop dimensions and spacing become smaller.

A lower frequency produces a longer wavelength, resulting in larger physical dimensions.

This relationship is fundamental to wavelength-based antenna design.

2. Number of Elements

The calculator supports 2 or 3 elements.

2-Element Configuration

A 2-element Cubical Quad contains:

1. Driven element
2. Reflector

The calculator provides:

• Wavelength
• Driven perimeter
• Driven side length
• Reflector perimeter
• Reflector side length
• Recommended spacing
• Estimated gain

3-Element Configuration

A 3-element Cubical Quad adds a director:

1. Reflector
2. Driven element
3. Director

The calculator additionally provides:

• Director perimeter
• Director side length

The estimated gain also changes according to the calculator's element-count model.

3. Velocity Factor

The velocity factor is a multiplier applied to the free-space wavelength in this calculator.

The calculator uses:

Adjusted wavelength = free-space wavelength × velocity factor

For example, if the free-space wavelength is 2 meters and the selected velocity factor is 0.95:

Adjusted wavelength = 2 × 0.95 = 1.9 m

Because all antenna dimensions in this calculator are derived from the adjusted wavelength, changing the velocity factor changes the resulting dimensions and spacing.

A velocity factor of 1.0 leaves the wavelength unchanged from the calculator's free-space calculation.

Users should select a velocity factor appropriate to what they are attempting to model rather than choosing a value simply to obtain a desired physical dimension.

Cubical Quad Antenna Formulas

Understanding the formulas makes it easier to interpret the calculator's results.

Wavelength Formula

The calculator uses:

λ = (300 / f) × VF

Here:

• λ represents the calculated wavelength in meters.
• f represents frequency in MHz.
• VF represents velocity factor.

The constant 300 is a rounded value used for the relationship between frequency in MHz and wavelength in meters.

Driven Element Formula

The calculator models the driven loop as one wavelength around its perimeter:

Driven perimeter = λ

Because the loop is treated as four equal sides:

Driven side = λ / 4

For example, if the calculated wavelength is 2 meters:

Driven perimeter = 2 m

Driven side = 2 / 4 = 0.5 m

Reflector Formula

The reflector is calculated as:

Reflector perimeter = 1.05 × λ

Its side length is:

Reflector side = reflector perimeter / 4

Therefore, the reflector is modeled with a perimeter 5% larger than the driven element.

Director Formula

The director is only calculated for a 3-element antenna.

The formula is:

Director perimeter = 0.95 × λ

Its side length is:

Director side = director perimeter / 4

This makes the modeled director smaller than the driven loop.

Element Spacing Formula

The calculator uses:

Spacing = 0.15 × λ

This produces a spacing value proportional to the calculated wavelength.

For example, with a wavelength of 2 meters:

Spacing = 0.15 × 2 = 0.3 m

Gain Estimation

The calculator provides a simple gain estimate based on the number of elements:

• 2 elements: 8.0 dBi
• 3 elements: 10.0 dBi

These values should be interpreted as calculator estimates, not guaranteed measured performance.

Actual antenna gain can vary depending on the antenna's construction, geometry, environment, losses, installation, and other factors.

Real-Life Example: Designing a 3-Element Cubical Quad for 144 MHz

Consider a radio operator who wants to build a 3-element Cubical Quad centered around 144 MHz.

The calculator inputs are:

• Frequency: 144 MHz
• Number of elements: 3
• Velocity factor: 1.0

Let's work through the calculator's model.

Step 1: Calculate Wavelength

The formula is:

λ = (300 / 144) × 1.0

This gives:

λ ≈ 2.083 m

So the calculator uses approximately 2.083 meters as the wavelength for the rest of the design.

Step 2: Calculate the Driven Element

The driven-element perimeter is one wavelength:

Driven perimeter = 2.083 m

The loop has four equal sides:

Driven side = 2.083 / 4

Driven side ≈ 0.521 m

Therefore, the calculator provides:

• Driven perimeter: 2.083 m
• Driven side length: 0.521 m

Step 3: Calculate the Reflector

The reflector perimeter is:

Reflector perimeter = 2.083 × 1.05

Reflector perimeter ≈ 2.188 m

The side length is:

Reflector side = 2.188 / 4

Reflector side ≈ 0.547 m

The calculator therefore gives an approximate reflector perimeter of 2.188 m and side length of 0.547 m.

Step 4: Calculate the Director

Because this is a 3-element design, the calculator calculates the director.

The director perimeter is:

Director perimeter = 2.083 × 0.95

Director perimeter ≈ 1.979 m

The side length becomes:

Director side = 1.979 / 4

Director side ≈ 0.495 m

So the modeled director has:

• Perimeter: 1.979 m
• Side length: 0.495 m

Step 5: Calculate Element Spacing

The calculator uses:

Spacing = 0.15 × 2.083

Spacing ≈ 0.313 m

The recommended spacing output is therefore approximately 0.313 meters.

Step 6: Estimated Gain

Because the design contains three elements, the calculator returns:

Estimated gain = 10.0 dBi

This is a simplified estimate produced by the calculator and should not be treated as a guaranteed measurement of the finished antenna.

Practical Interpretation

The resulting design gives the builder an initial dimensional reference:

A builder can use these values during the initial planning stage, then validate and tune the physical antenna after construction.

Real-World Use Cases for the Cubical Quad Antenna Calculator

Amateur Radio Antenna Construction

One of the most practical uses is early-stage amateur radio antenna design.

A hobbyist can enter a target frequency and immediately obtain wavelength-based dimensions for a 2- or 3-element Cubical Quad.

This can help with initial planning before purchasing materials or constructing the support structure.

2-Element Quad Design

When simplicity is important, the calculator can be used to develop a basic 2-element design.

The user receives dimensions for:

• Driven loop
• Reflector loop
• Element spacing

This provides a starting framework without requiring manual calculations for every dimension.

3-Element Directional Quad Design

A user who wants to experiment with a three-element configuration can select 3 in the element field.

The calculator then adds the director calculations automatically.

This makes it useful for comparing a basic 2-element concept with a more complex 3-element design.

Educational Antenna Projects

The calculator can also be useful for learning the relationship between frequency and physical antenna dimensions.

For example:

Frequency → wavelength → loop perimeter → side length → spacing

Students and hobbyists can change the frequency and immediately see how the physical dimensions change.

Rapid Design Iteration

The calculator is particularly useful when comparing different target frequencies.

For example, a designer can calculate a Cubical Quad at 50 MHz and then calculate another at 144 MHz.

The results demonstrate how the higher-frequency design requires smaller wavelength-based dimensions.

This makes the tool useful during the early design and experimentation phase.

2-Element vs. 3-Element Cubical Quad

The calculator supports two configurations.

A 2-element design can be a useful starting point when the goal is a simpler antenna structure.

A 3-element design adds a director and therefore introduces another physical loop and additional support requirements. In the calculator's simplified gain model, it also receives a higher estimated gain.

However, the difference between the calculator's gain estimates and actual antenna performance should be kept clear. Real-world performance cannot be determined from element count alone.

Understanding Cubical Quad Antenna Dimensions

Frequency has a direct impact on the dimensions calculated by this tool.

When Frequency Increases

As frequency increases, wavelength becomes shorter.

That means:

• Driven loop becomes smaller
• Reflector becomes smaller
• Director becomes smaller
• Element spacing becomes smaller

For example, the calculated wavelength at 144 MHz is approximately 2.083 m when the velocity factor is 1.0.

When Frequency Decreases

When frequency decreases, wavelength increases.

That means:

• Loop dimensions increase
• Reflector dimensions increase
• Director dimensions increase
• Element spacing increases

For example, at 50 MHz with a velocity factor of 1.0:

λ = 300 / 50 = 6 m

That is substantially longer than the approximately 2.083 m wavelength calculated at 144 MHz.

This is why antenna designs for lower frequencies can become physically much larger.

Understanding Element Spacing

The calculator uses:

Element spacing = 0.15 × wavelength

This provides a wavelength-based starting reference for positioning the antenna elements.

For the 144 MHz example:

Spacing ≈ 0.313 m

This means the calculator recommends approximately 31.3 cm based on its implemented formula.

It is important to understand that this is a calculator-specific design value, not a universal spacing rule that automatically produces optimal performance for every Cubical Quad.

The final antenna can be affected by factors such as:

• Physical construction
• Supporting structures
• Nearby conductive objects
• Installation environment
• Feed arrangement
• Element geometry

For this reason, spacing should be treated as an initial design reference rather than a guarantee of final antenna performance.

What Does Velocity Factor Mean in This Calculator?

Velocity factor changes the wavelength used by the calculator.

Suppose the frequency is 144 MHz.

With a velocity factor of 1.0:

λ = 300 / 144 × 1.0

λ ≈ 2.083 m

If the velocity factor is changed to 0.95:

λ = 300 / 144 × 0.95

λ ≈ 1.979 m

Because the loop dimensions and spacing are derived from this wavelength, they also become smaller.

For example, the driven side changes from approximately:

0.521 m

to approximately:

0.495 m

when moving from a velocity factor of 1.0 to 0.95.

This illustrates why velocity factor should be selected intentionally rather than arbitrarily.

How to Read the Calculator Results

After calculation, the tool provides several outputs.

Wavelength

This is the calculated wavelength used as the foundation for the remaining dimensions.

Driven Element Perimeter

This is the total perimeter of the driven loop.

The calculator sets it equal to one wavelength.

Driven Element Side Length

This represents one quarter of the driven-element perimeter.

Reflector Perimeter

This is the modeled reflector loop perimeter.

The calculator sets it to 1.05 wavelengths.

Reflector Side Length

This is one quarter of the reflector perimeter.

Recommended Element Spacing

This is calculated using:

0.15 × wavelength

Director Perimeter

This is only displayed when three elements are selected.

The calculator sets it to 0.95 wavelengths.

Director Side Length

This is one quarter of the director perimeter.

Estimated Gain

This is the simplified gain estimate based on element count:

• 2 elements: 8.0 dBi
• 3 elements: 10.0 dBi

Construction Considerations Before Building

Calculator results are valuable during the design stage, but a physical antenna involves more variables than the mathematical model.

Conductor Material

The actual conductor used for the loops can affect the electrical behavior of the finished antenna. Wire, tubing, and other conductor configurations may behave differently.

Physical Dimensions

The calculator's values are starting dimensions based on its formulas. They should not automatically be assumed to be final tuned dimensions.

Feed Point

The driven element needs an appropriate feed arrangement for the intended radio system. The feed configuration is not modeled by this calculator.

Support Structure

A Cubical Quad requires a physical structure capable of maintaining the loop geometry and element spacing.

Depending on the design, this may involve:

• Boom or central support
• Spreaders
• Insulators
• Element attachment points

Installation Environment

Nearby structures can influence the behavior of an antenna.

Potential influences include:

• Buildings
• Trees
• Metal structures
• Other antennas
• Conductive objects

Therefore, an antenna that performs one way in an open test environment may behave differently after installation.

Measurement and Tuning

After construction, the antenna should be evaluated using appropriate measurement equipment and adjusted where necessary.

The calculator is most useful as a design starting point, not as a replacement for physical validation.

Cubical Quad Antenna Calculator vs. Manual Calculation

Without a calculator, designing the basic dimensions requires several individual calculations.

A typical manual process would be:

1. Calculate wavelength.
2. Apply the velocity factor.
3. Calculate driven-element perimeter.
4. Divide the driven perimeter by four.
5. Calculate reflector perimeter.
6. Divide the reflector perimeter by four.
7. If using three elements, calculate director perimeter.
8. Divide director perimeter by four.
9. Calculate element spacing.
10. Determine the calculator's estimated gain.

The Cubical Quad Antenna Calculator automates these steps.

Instead of repeatedly working through the formulas, you enter:

• Frequency
• Number of elements
• Velocity factor

The tool then returns the corresponding dimensions.

This is particularly useful when experimenting with multiple frequencies or comparing different 2-element and 3-element configurations.

Common Cubical Quad Antenna Design Mistakes

Mistake 1: Confusing Perimeter With Side Length

A loop perimeter represents the total distance around the loop.

It is not the length of one side.

For the calculator's square-loop model:

Side length = perimeter / 4

Mistake 2: Ignoring Velocity Factor

If you intentionally use a velocity factor below 1.0, it changes the calculated wavelength and consequently changes all dimensions derived from that wavelength.

Mistake 3: Selecting the Wrong Number of Elements

The calculator supports only two configurations:

• 2 elements
• 3 elements

A 2-element design does not receive director calculations.

A 3-element design includes a director.

Mistake 4: Treating Estimated Gain as Guaranteed Performance

The calculator returns:

8.0 dBi for 2 elements

and

10.0 dBi for 3 elements

These values are estimates from the calculator's simplified model. They should not be interpreted as guaranteed measured gain for a finished antenna.

Mistake 5: Assuming the Calculated Dimensions Are Final

A mathematical starting point does not automatically account for every detail of a real antenna installation.

Construction, environment, feed system, and tuning can all affect the final result.

Frequently Asked Questions

What is a Cubical Quad antenna?

A Cubical Quad is a directional antenna that uses loop-shaped elements supported by a structural framework. The loops can function as driven, reflector, and director elements.

What does a Cubical Quad Antenna Calculator calculate?

It calculates wavelength, driven-element dimensions, reflector dimensions, director dimensions for a 3-element design, recommended element spacing, and estimated gain.

How is wavelength calculated?

This calculator uses:

λ = (300 / f) × VF

where frequency is expressed in MHz and velocity factor is a unitless multiplier.

What is the driven element size?

The calculator sets the driven-element perimeter equal to one calculated wavelength.

Its side length is:

Driven side = wavelength / 4

How large is the reflector?

The calculator uses:

Reflector perimeter = 1.05 × wavelength

The reflector side length is one quarter of that perimeter.

How large is the director?

For a 3-element design, the calculator uses:

Director perimeter = 0.95 × wavelength

The director side length is one quarter of its perimeter.

What is the recommended element spacing?

The calculator uses:

Spacing = 0.15 × wavelength

This should be considered a starting design value.

How many elements does the calculator support?

It supports 2 or 3 elements.

What is the estimated gain?

The calculator estimates:

• 8.0 dBi for 2 elements
• 10.0 dBi for 3 elements

These are simplified calculator estimates rather than guaranteed real-world measurements.

Can I calculate a 144 MHz Cubical Quad?

Yes. Enter 144 MHz, select either 2 or 3 elements, and enter the desired velocity factor.

With 3 elements and a velocity factor of 1.0, the calculator produces a wavelength of approximately 2.083 m.

Does velocity factor change antenna dimensions?

Yes. In this calculator, velocity factor directly scales the calculated wavelength. Since the element dimensions and spacing are derived from wavelength, changing the velocity factor changes those results as well.

Are the calculated dimensions final construction dimensions?

No. The results should be treated as initial design dimensions. A completed antenna may require measurement and tuning based on its actual construction and installation environment.

Cubical Quad Antenna Formula Quick Reference

This formula set provides the mathematical foundation for the calculator's outputs.

Practical Cubical Quad Antenna Design Workflow

Designing a Cubical Quad with this calculator can be approached in eight simple steps.

1. Choose the Operating Frequency

Determine the frequency around which the antenna will be designed.

2. Enter the Frequency

Enter the frequency in MHz.

3. Select the Element Count

Choose either 2 or 3 elements.

4. Enter the Velocity Factor

Select a value from 0.8 to 1.0 appropriate for your intended calculation.

5. Calculate the Dimensions

Review the wavelength, loop perimeters, side lengths, spacing, and estimated gain.

6. Plan the Physical Structure

Use the calculated dimensions as initial references when planning the loops, spreaders, boom, and other support components.

7. Build the Antenna

Construct the antenna according to your physical design and selected materials.

8. Measure and Tune

Evaluate the finished antenna and make adjustments where necessary.

This workflow separates initial mathematical design from real-world antenna validation, which is important when converting calculated dimensions into a working antenna.

Final Takeaway

The Cubical Quad Antenna Calculator provides a convenient way to convert operating frequency into practical starting dimensions for a 2-element or 3-element Cubical Quad antenna.

By entering the frequency, number of elements, and velocity factor, you can calculate:

• Wavelength
• Driven-element perimeter
• Driven-element side length
• Reflector perimeter
• Reflector side length
• Director perimeter for 3-element designs
• Director side length
• Recommended element spacing
• Estimated gain

The calculator uses a simplified model in which the driven element is one wavelength around its perimeter, the reflector is 1.05 wavelengths, and the director is 0.95 wavelengths. Element spacing is calculated as 0.15 wavelength.

For a practical antenna project, these values are best treated as initial design references. The final antenna can behave differently depending on its construction, feed system, surroundings, support structure, and installation conditions.

Enter your operating frequency, choose 2 or 3 elements, select an appropriate velocity factor, and use the calculated dimensions as the starting point for your Cubical Quad antenna project.