Moxon Antenna Calculator

The Moxon Antenna Calculator helps you estimate the basic dimensions of a Moxon Rectangle antenna from its operating frequency. Enter the frequency in MHz, and the calculator estimates the wavelength, driven element length, reflector length, overall width, overall height, and feed impedance.

The calculator uses simple wavelength-based formulas. This makes it useful when you want a quick starting point for a DIY antenna project.

For example, if you enter 144 MHz, the calculator first determines the wavelength. It then uses fixed proportions of that wavelength to estimate the main antenna dimensions.

The results are approximate. A real antenna may need adjustment after construction because factors such as conductor size, element spacing, mounting conditions, nearby objects, and the physical installation can affect its actual behavior.

What Is a Moxon Antenna?

A Moxon antenna, also called a Moxon Rectangle, is a compact directional antenna design used in radio applications. Its basic structure contains a driven element and a reflector arranged in a rectangular shape.

The geometry is different from a simple straight dipole. The elements are bent toward each other, which allows the antenna to maintain a relatively compact physical form.

A Moxon antenna can be useful for amateur radio operators, RF hobbyists, antenna experimenters, and DIY builders who want to work with a directional antenna design.

The exact dimensions depend on the operating frequency. This is where a Moxon antenna calculator becomes useful.

Instead of calculating every dimension manually, you can enter your desired frequency and get a set of approximate starting dimensions.

The calculator described on this page provides six outputs:

• Wavelength
• Driven Element Length
• Reflector Length
• Overall Width
• Overall Height
• Estimated Feed Impedance

These values give you a starting point for antenna design and construction.

It is important to understand that the calculator does not perform a full electromagnetic simulation. It uses the formulas defined in the calculator to produce approximate dimensions.

How the Moxon Antenna Calculator Works

The calculator starts with the operating frequency.

The frequency must be entered in MHz. For example:

• 7.1 MHz
• 14.2 MHz
• 28.4 MHz
• 50 MHz
• 144 MHz

The first calculation determines the wavelength.

Wavelength Formula

The calculator uses:

λ = 300 ÷ f

Where:

• λ is wavelength in meters
• f is frequency in MHz

Once the wavelength is known, the calculator applies the following proportions.

Driven Element

The calculator estimates the driven element as:

Driven Element ≈ λ × 0.48

Reflector

The reflector is estimated as:

Reflector ≈ λ × 0.50

Overall Width

The calculator estimates:

Width ≈ λ × 0.33

Overall Height

The calculator estimates:

Height ≈ λ × 0.17

Estimated Feed Impedance

The calculator returns:

50 ohms

This should be treated as an estimated design value. It does not mean that a completed physical antenna will automatically measure exactly 50 ohms.

Moxon Antenna Calculator Formula

The calculation process is straightforward.

First, calculate wavelength:

λ = 300 / f

Then calculate each dimension:

For example, when the frequency is 144 MHz:

Wavelength = 300 ÷ 144 = 2.083 m

The calculator then applies its fixed multipliers to this wavelength.

This approach makes the calculator fast and easy to use. You do not need to perform several separate calculations with a calculator or spreadsheet.

How to Use the Moxon Antenna Calculator

Using the calculator requires only one input.

Step 1: Choose Your Operating Frequency

Determine the frequency you want the antenna to operate around.

For example:

144 MHz

Step 2: Enter the Frequency

Enter 144 into the frequency field.

Make sure the unit is MHz.

Step 3: Calculate the Results

The calculator determines the wavelength and applies the formulas to estimate the antenna dimensions.

Step 4: Review the Wavelength

The wavelength gives you the fundamental dimension used by the remaining calculations.

Step 5: Review the Antenna Dimensions

The calculator provides:

• Driven element length
• Reflector length
• Overall width
• Overall height

These dimensions can then be used as initial construction values.

Step 6: Build and Test

After construction, measure the antenna using appropriate RF measurement equipment.

If the measured behavior differs from your target, the physical antenna may require adjustment.

The calculator is therefore best viewed as the first stage of the antenna design process rather than the final tuning system.

Real-Life Example: Designing a 144 MHz Moxon Antenna

Imagine an amateur radio operator wants to experiment with a Moxon antenna around 144 MHz.

The operator wants to know the approximate physical size before purchasing materials and building the antenna.

They enter:

Frequency = 144 MHz

Step 1: Calculate Wavelength

The calculator uses:

λ = 300 ÷ 144

Therefore:

λ ≈ 2.083 meters

The wavelength is approximately 2.083 m.

Step 2: Calculate the Driven Element

The calculator uses:

Driven Element = λ × 0.48

So:

2.083 × 0.48 ≈ 1.000 m

The estimated driven element length is approximately:

1.000 m

Step 3: Calculate the Reflector

The reflector formula is:

Reflector = λ × 0.50

Therefore:

2.083 × 0.50 ≈ 1.042 m

The estimated reflector length is approximately:

1.042 m

Step 4: Calculate Overall Width

The calculator uses:

Width = λ × 0.33

Therefore:

2.083 × 0.33 ≈ 0.688 m

The estimated overall width is approximately:

0.688 m

Step 5: Calculate Overall Height

The formula is:

Height = λ × 0.17

Therefore:

2.083 × 0.17 ≈ 0.354 m

The estimated overall height is approximately:

0.354 m

144 MHz Example Results

This gives the operator a useful starting point for physical planning.

Before construction, they can use these dimensions to determine how much conductive material and support material may be required.

After building the antenna, they can measure its actual RF characteristics and make adjustments where necessary.

A Practical Moxon Antenna Use Case

Consider a hobbyist planning a temporary antenna installation.

They have limited space and want to know whether a Moxon design based on their target frequency can physically fit in the available area.

Instead of purchasing materials first, they can use the calculator to estimate the dimensions.

The workflow might look like this:

1. Select the operating frequency.
2. Enter the frequency into the calculator.
3. Calculate the wavelength.
4. Check the estimated driven element.
5. Check the reflector length.
6. Check the overall width.
7. Check the overall height.
8. Compare those dimensions with the available installation space.
9. Plan the support structure.
10. Build the antenna.
11. Measure the completed antenna.
12. Tune it if necessary.

This can reduce guesswork during the planning stage.

For example, a portable radio operator can calculate the approximate antenna size before deciding whether the design is suitable for a particular mast, support, or field setup.

The same process can help a DIY antenna builder estimate material requirements before beginning construction.

Comparing Moxon Antenna Dimensions at Different Frequencies

Because the calculator is based on wavelength, changing frequency changes every calculated dimension.

Consider these examples:

These values demonstrate the basic relationship between frequency and the calculated antenna dimensions.

At lower frequencies, the calculated wavelength is larger. At higher frequencies, the calculated wavelength becomes smaller.

This is why selecting the correct operating frequency is critical when using a Moxon antenna calculator.

Understanding the Calculator Outputs

Wavelength

Wavelength is the first value calculated by the tool.

It represents the wavelength associated with the frequency entered by the user.

The calculator expresses wavelength in meters.

This value is then used to calculate the other dimensions.

Driven Element Length

The driven element is the part of the antenna connected to the feed system.

In this calculator, its estimated length is:

0.48 × wavelength

The result is provided in meters.

Reflector Length

The reflector is another major part of the Moxon geometry.

The calculator estimates its length using:

0.50 × wavelength

Again, this is an approximate starting value.

Overall Width

The calculator estimates overall width using:

0.33 × wavelength

This value is particularly useful when planning the physical footprint of the antenna.

Overall Height

The calculator estimates overall height using:

0.17 × wavelength

This helps the builder understand the approximate physical size of the design.

Estimated Feed Impedance

The calculator returns:

50 ohms

Feed impedance describes the electrical impedance presented at the feed point.

However, the value shown by this calculator is an estimate. Actual impedance depends on the physical antenna and its environment.

A completed antenna should be measured rather than assuming the calculated value is the measured value.

Moxon Antenna Construction Considerations

The calculator provides mathematical estimates. Building the physical antenna introduces additional variables.

Conductor Diameter

The diameter of the conductor can influence the electrical behavior of an antenna.

Therefore, the final antenna may not behave exactly like the simplified calculation.

Element Geometry

The physical shape and spacing need to be built carefully.

Small construction differences can change the resulting antenna characteristics.

Construction Material

A Moxon antenna can be constructed using suitable conductive materials such as wire or metal tubing, depending on the design and mechanical requirements.

The chosen material should also provide enough mechanical strength for the intended installation.

Feed Point

The feed point needs to be mechanically secure and electrically appropriate.

Good construction practice is important because loose connections or poor mechanical support can affect testing and long-term reliability.

Installation Environment

The surrounding environment can affect an antenna.

Nearby structures may include:

• Buildings
• Metal structures
• Towers
• Cables
• Trees
• Other antennas
• Ground or roofing materials

For this reason, an antenna that performs one way during an indoor or temporary test may behave differently after installation.

Why Calculated Dimensions May Differ From the Final Antenna

One of the most important things to understand about an antenna calculator is the difference between calculation and real-world measurement.

This calculator uses fixed ratios:

• 0.48λ for the driven element
• 0.50λ for the reflector
• 0.33λ for width
• 0.17λ for height

These formulas provide a consistent starting point.

A real antenna, however, exists in a physical environment.

Its behavior can be influenced by:

• conductor diameter
• element spacing
• feedline position
• mounting height
• nearby conductive objects
• construction accuracy
• antenna orientation
• surrounding structures

Therefore, the dimensions generated by the calculator should not automatically be treated as final tuned dimensions.

A practical antenna-building process normally involves calculating initial dimensions, constructing the antenna, measuring it, and making controlled adjustments when necessary.

How to Improve Moxon Antenna Accuracy

A practical workflow can be summarized as:

Calculate → Build → Measure → Tune → Re-measure

Calculate

Use the Moxon Antenna Calculator to establish the initial dimensions.

Build

Construct the antenna as accurately as practical.

Measure

Use an appropriate antenna analyzer or RF measurement system to evaluate the completed antenna.

Tune

If the antenna does not behave as expected, make controlled physical adjustments.

Re-measure

Measure the antenna again after each meaningful adjustment.

This process is more reliable than assuming that a mathematical estimate will perfectly match every physical installation.

Moxon Antenna Calculator vs Manual Calculation

You can calculate antenna dimensions manually, but doing so repeatedly can become time-consuming.

The calculator automates the arithmetic.

The Moxon Antenna Calculator is therefore best suited to quick design estimation.

It is not intended to replace detailed electromagnetic modeling or physical measurement.

Common Moxon Antenna Calculator Mistakes

Entering the Wrong Frequency

The frequency input has a major effect on the result.

Entering 144 MHz produces completely different dimensions from entering 14.4 MHz.

Always verify the operating frequency before calculating.

Mixing Units

The calculator provides dimensions in meters.

If you build using centimeters, millimeters, or feet, convert the values carefully.

For example:

1 meter = 100 centimeters

Treating the Results as Exact

The calculator provides approximate dimensions based on its formulas.

Do not assume that the resulting dimensions automatically represent the final tuned antenna.

Ignoring the Installation Environment

The surrounding environment can influence the completed antenna.

Consider nearby conductive structures before final installation.

Assuming 50 Ohms Is Guaranteed

The calculator reports an estimated feed impedance of 50 ohms.

That is not the same as measuring 50 ohms at the completed antenna's feed point.

Making Permanent Construction Too Early

If you expect to tune the antenna, make the construction method suitable for controlled adjustments before permanently fixing every dimension.

Moxon Antenna Calculator Quick Reference

The calculator requires only frequency as an input.

Everything else is generated from that value.

Practical Workflow From Frequency to Finished Antenna

A complete project can follow this process:

1. Select the target operating frequency.
2. Enter the frequency in MHz.
3. Calculate the wavelength.
4. Calculate the driven element length.
5. Calculate the reflector length.
6. Calculate the overall width.
7. Calculate the overall height.
8. Review the estimated physical footprint.
9. Select appropriate construction materials.
10. Build the antenna.
11. Connect the feed system.
12. Measure the completed antenna.
13. Tune the physical dimensions if required.
14. Measure again.
15. Record the final construction dimensions.

This workflow separates initial design calculations from real-world antenna tuning.

Who Can Use a Moxon Antenna Calculator?

The calculator can be useful for several types of users.

Amateur Radio Operators

Ham radio operators can use it to quickly estimate starting dimensions for an antenna project.

Beginners

New antenna builders can use it to understand how frequency and wavelength are related.

RF Hobbyists

RF enthusiasts can use the tool when experimenting with different frequencies and antenna dimensions.

Electronics Students

The calculator can provide a practical example of how a frequency value can be converted into physical dimensions.

DIY Antenna Builders

Builders can use the results when planning materials, supports, and installation space.

Moxon Antenna Calculator Limitations

The calculator has a clearly defined scope.

It calculates:

• Wavelength
• Driven element length
• Reflector length
• Overall width
• Overall height
• Estimated feed impedance

It does not calculate, based on the provided implementation:

• Antenna gain
• Front-to-back ratio
• Radiation pattern
• SWR
• Bandwidth
• Element gap
• Conductor diameter
• Mounting height
• Takeoff angle
• Transmission-line loss
• Detailed electromagnetic field behavior

This distinction matters.

The calculator is a quick dimension estimator, not a complete antenna modeling platform.

Its results should be used as initial design values and then validated through appropriate physical testing.

Frequently Asked Questions

What is a Moxon Antenna Calculator?

A Moxon Antenna Calculator is a frequency-based tool that estimates the dimensions of a Moxon Rectangle antenna. This calculator uses operating frequency to calculate wavelength and then estimates the driven element, reflector, overall width, overall height, and feed impedance.

How do you calculate Moxon antenna dimensions?

First calculate the wavelength using:

λ = 300 ÷ frequency in MHz

Then apply the calculator's dimension ratios:

• Driven element = 0.48λ
• Reflector = 0.50λ
• Width = 0.33λ
• Height = 0.17λ

What formula does this Moxon calculator use?

The primary formula is:

λ = 300 / f

The calculator then applies fixed wavelength multipliers to estimate the main antenna dimensions.

What frequency should I enter?

Enter the operating frequency in MHz.

For example, if your target frequency is 144 MHz, enter:

144

What does 300 divided by frequency calculate?

In this calculator, 300 / frequency provides an approximate wavelength in meters when frequency is expressed in MHz.

What is the Moxon driven element?

The driven element is the antenna element connected to the feed system. In this calculator, its approximate length is calculated as 0.48 times the wavelength.

What is the Moxon reflector?

The reflector is another major element in the Moxon antenna structure. This calculator estimates its length as 0.50 times the wavelength.

Does this calculator provide exact Moxon antenna dimensions?

No. It provides approximate dimensions based on the formulas implemented in the calculator. The final physical antenna may require adjustment after construction and measurement.

Is the Moxon antenna feed impedance 50 ohms?

This calculator uses 50 ohms as its estimated feed impedance. However, this does not guarantee that a physical antenna will measure exactly 50 ohms. Actual impedance should be measured on the completed antenna.

Can I use this calculator for 144 MHz?

Yes. Enter 144 MHz as the frequency. The calculator produces an approximate wavelength of 2.083 m and uses that value to calculate the other dimensions.

Can I use the calculator for other frequencies?

Yes. The calculator accepts positive frequency values in MHz. The resulting dimensions change according to the calculated wavelength.

Do I need to tune a Moxon antenna after building it?

The calculator's output should be treated as an initial design estimate. A physical antenna can behave differently because of construction and installation conditions, so measurement and adjustment may be appropriate.

Final Thoughts

The Moxon Antenna Calculator provides a fast way to estimate the basic dimensions of a Moxon Rectangle antenna from operating frequency.

Its calculation process is simple. Enter the frequency in MHz, calculate the wavelength, and apply the predefined proportions for the driven element, reflector, width, and height.

For a 144 MHz example, the calculator produces an approximate wavelength of 2.083 meters, a 1.000-meter driven element, a 1.042-meter reflector, a 0.688-meter overall width, and a 0.354-meter overall height.

These values provide a practical starting point for antenna planning and construction.

However, the calculated dimensions should not be treated as guaranteed final specifications. Real-world antenna performance can depend on construction details and the surrounding installation environment.

For the best practical workflow, use the calculator to establish initial dimensions, build the antenna carefully, measure the finished antenna, and tune it when necessary.

Enter your operating frequency into the Moxon Antenna Calculator to generate your approximate starting dimensions.