Advanced Antenna Height Calculator

Calculation Results

Results update after calculation and appear before the form.

Awaiting input

Transmitter horizon—

Receiver horizon—

Combined radio horizon—

Required transmitter height—

Midpoint Fresnel radius—

Midpoint Earth bulge—

Critical clearance margin—

Recommended installation height—

Transmitter AMSL—

Receiver AMSL—

Critical obstruction—

Average HAAT—

Import scenario

No calculation has been completed.

Calculator Inputs

Use the tabs to configure the link, environment, obstacles, HAAT, and comparison scenarios.

Link and antenna configuration

System preset

Calculation mode

Operating frequency

Link distance

Transmitter antenna height AGL

Receiver antenna height AGL

Transmitter ground elevation AMSL

Receiver ground elevation AMSL

Mounting and cable allowance

Maximum permitted tower height

Result height unit

Result distance unit

Decimal precision

Atmospheric, curvature, and clearance settings

Earth-radius factor

Custom K-factor

Required Fresnel clearance

General safety clearance

Vegetation growth allowance

Terrain and installation uncertainty

Future clearance reserve

Earth radius

Enable live calculation

Terrain and obstruction profile

Add obstacles manually or import rows from a CSV file.

Import terrain CSV

Name	Distance from transmitter	Ground elevation	Obstacle height	Extra allowance	Action

CSV columns: name, distance_km, ground_elevation_m, obstacle_height_m, extra_allowance_m.

Height above average terrain

Radial count

Terrain averaging start

Terrain averaging end

Terrain elevations by radial

Enter one radial per line. Start each line with azimuth, followed by terrain elevations in metres.

Scenario comparison

Store the current result and compare frequencies, heights, margins, and status.

Scenario	Frequency	Distance	Tx height	Rx height	Critical margin	Status
No scenarios stored.

Link Path Profile

The chart shows terrain, line of sight, Earth curvature, Fresnel boundaries, towers, and critical clearance.

Obstruction Clearance Report

Obstacle	Distance	Top elevation	Earth bulge	Required Fresnel	Available clearance	Margin	Status
Calculate to generate the report.

Formula Used

Radio horizon: d = √(2 × K × R × h).
First Fresnel radius: F₁ = √(λ × d₁ × d₂ ÷ (d₁ + d₂)).
Earth bulge: b = d₁ × d₂ ÷ (2 × K × R).
HAAT: antenna radiation-centre AMSL minus average terrain elevation.

Distances use metres during every internal calculation. Heights use metres before output conversion. Frequency is converted to hertz automatically.

The effective Earth radius equals K times Earth radius. A lower K-factor increases apparent curvature. A higher K-factor reduces apparent curvature.

Fresnel clearance uses the selected percentage and safety allowances. Terrain values remain referenced to mean sea level. Review local regulations before final tower construction decisions carefully.

How to Use

Select a system preset or enter custom values. Add transmitter and receiver elevations. Choose consistent or mixed input units.

Set atmospheric refraction and Fresnel clearance requirements. Add every important terrain obstacle. Include future vegetation and installation reserves.

Press calculate and inspect the critical obstruction. Compare the chart with the clearance table. Export the report for engineering review and documentation.

Example Data

Field	Example	Purpose
Frequency	5.8 GHz	Controls wavelength and Fresnel radius.
Link distance	12 km	Sets the transmitter-to-receiver path.
Transmitter height	30 m AGL	Defines the starting radiation-centre height.
Receiver height	12 m AGL	Defines the ending radiation-centre height.
K-factor	1.3333	Models standard atmospheric refraction.
Fresnel clearance	60%	Sets the required propagation clearance.

Assumptions and Limitations

This calculator provides geometric planning estimates only. It does not replace a certified site survey. Terrain accuracy depends on entered data.

Atmospheric refraction varies with weather and location. Multipath effects require separate propagation modelling. Structural tower design remains outside this calculator.

Regulatory limits may restrict antenna location and height. Always verify local aviation and communications rules. Confirm final measurements with qualified engineering professionals onsite.

Frequently Asked Questions

What is antenna height AGL?

AGL means height above local ground level. It excludes the site elevation above sea level. Use the antenna radiation centre whenever available.

What is antenna height AMSL?

AMSL means height above mean sea level. Add ground elevation and antenna height AGL. This reference supports terrain profile comparisons.

Why does frequency affect clearance?

Frequency determines wavelength and Fresnel-zone size. Lower frequencies create larger Fresnel zones. Larger zones usually require more vertical clearance.

What Fresnel percentage should I use?

Sixty percent is a common planning target. Difficult links may need larger margins. Follow the applicable engineering standard and environment.

What does the K-factor represent?

The K-factor models atmospheric bending of radio waves. Standard planning often uses four-thirds Earth radius. Adverse conditions can require lower values.

How is Earth bulge calculated?

Earth bulge depends on both path segments. It is greatest near the midpoint. Effective Earth radius includes the selected K-factor.

Can I import terrain data?

Yes, import a CSV with the documented columns. Distances must remain inside the link path. Elevations and heights should use metres.

What is the critical obstruction?

It is the obstacle with the smallest clearance margin. Negative margin indicates insufficient planned clearance. Raise an antenna or reduce the obstruction.

Does this calculate structural tower strength?

No, it only estimates geometric and radio clearance. Wind loading needs structural engineering calculations. Use certified designs for every final installation.