Enter Antenna and Site Data
Use manufacturer-approved antenna data whenever it is available. Inputs marked as comparison values are optional.
Example Data Table
| Input | Example value | Purpose |
|---|---|---|
| Basic wind speed | 115 mph | Project wind speed before local adjustments. |
| Exposure category | C | Representative open terrain condition. |
| Centerline height | 60 ft | Used to estimate automatic Kz. |
| Projected area | 8.50 ft² | One antenna effective projected area. |
| Force coefficient | 1.20 | Applied aerodynamic force coefficient. |
| Ice multiplier | 1.00 | No added ice area for this example. |
| Load multiplier | 1.00 | Service-level illustration only. |
Formula Used
qz = 0.00256 × V² × Kz × Kzt × Kd
Ae = A × N × Mi
Fservice = qz × G × Cf × Ae
Fdesign = Fservice × Lm
M = Fdesign × (H + e)
V is wind speed in mph. qz is velocity pressure in psf. Kz, Kzt, and Kd are exposure, topographic, and directionality factors. A is projected area per antenna. N is antenna quantity. Mi is the ice multiplier. G is gust factor. Cf is force coefficient. Lm is applied load multiplier. H is centerline height. e is mount eccentricity.
The automatic Kz is a screening estimate based on antenna height and exposure category. It uses Kz = 2.01(z/zg)2/α, with a 15-foot minimum height. Use the exact coefficient required by the governing design standard for final work.
How to Use This Calculator
- Select US customary or Metric SI before entering values.
- Enter the governing site wind speed and exposure category.
- Enter the antenna centerline height from the chosen support reference.
- Choose automatic Kz or enter the approved manual coefficient.
- Enter supplier projected area, quantity, drag coefficient, and any ice adjustment.
- Use the approved load multiplier for the selected design combination.
- Optionally enter support capacity and antenna rating for quick comparisons.
- Review force, moment, utilization, and notes before exporting results.
Wind Loading Considerations
Why Antenna Wind Load Matters
Kathrein antenna systems can present significant wind area on towers, poles, rooftops, and building facades. The load does not depend on antenna weight alone. Wind pressure rises with the square of wind speed. A modest speed increase can therefore create a much larger horizontal force. Mounting height also matters. Higher locations commonly experience stronger exposure. Direction, terrain, topography, gust effects, and ice can change the result. Use the manufacturer projected area or published force data for the exact antenna model. Do not substitute a face dimension when the supplier specifies an effective wind area.
What the Calculation Represents
This calculator uses a velocity pressure method. It converts the entered wind speed into pressure, then applies exposure, topographic, directionality, gust, and antenna force coefficients. The pressure is multiplied by the total projected area. A load multiplier can then be applied for the intended design check. The calculated force represents horizontal wind action. It is not a complete tower analysis. Connections, brackets, fasteners, pole bending, foundation capacity, fatigue, vibration, and combined equipment loads still need separate review.
Choosing Reliable Inputs
Select the unit system first. Enter the basic design wind speed required by the governing local standard. Choose the exposure category that most closely matches site conditions. Enter antenna centerline height above the support reference point. Add the projected area for one antenna and the number of identical antennas. Use an ice multiplier only when the project wind and ice criteria require it. Enter a supplied force coefficient when the applicable design method needs one. The default values are starting points, not project approvals.
Reviewing the Output
The output lists velocity pressure, effective area, force per antenna, total service force, adjusted design force, and overturning moment. Compare the adjusted force with the entered support capacity or manufacturer wind-load rating when those values are available. A utilization above one hundred percent signals that the entered limit is exceeded. A lower utilization is not a certification of adequacy. Confirm load combinations, installation orientation, eccentricity, cable loads, allowable stresses, and local permitting requirements. Have a qualified structural engineer approve the final design before equipment installation. Keep records of inputs and revisions for later maintenance checks. Small changes in antenna count, azimuth, mounting elevation, or dish accessories can alter demand. Recalculate whenever equipment changes, and retain manufacturer documents with the approved structural package for site records.
Frequently Asked Questions
1. What projected area should I enter?
Enter the manufacturer-specified projected area or equivalent wind area for the exact antenna model. Use the value for the proposed orientation. Do not estimate from cabinet dimensions when supplier wind data is available.
2. Can this calculator select a Kathrein antenna model?
No. It evaluates user-entered antenna data. Obtain projected area, wind rating, and mounting limits from the correct product documentation for the installed model.
3. Why does wind speed have such a large effect?
Velocity pressure changes with the square of wind speed. Doubling wind speed can create roughly four times the pressure before other factors are applied.
4. What is the purpose of Kz?
Kz adjusts wind pressure for height and exposure. The automatic value is useful for screening. Final calculations should use the coefficient and method required by the applicable structural standard.
5. When should I use a manual Kz value?
Use manual Kz when a project engineer, code table, or approved calculation provides it. Select manual mode so the calculator does not use its approximate automatic height and exposure relationship.
6. Does the ice multiplier model actual ice geometry?
No. It scales projected area as a planning adjustment. Projects with specified ice thickness, concurrent wind, or radial ice requirements need a detailed code-based geometry and load check.
7. Is the force coefficient always 1.20?
No. The correct force coefficient depends on antenna geometry, shielding, code method, and product data. The default is only an editable starting value.
8. What does the support utilization mean?
It divides calculated design force by the optional entered support capacity. More than 100 percent exceeds that entered limit. It does not evaluate moment capacity, connection capacity, or other structural checks.
9. Why is overturning moment included?
Wind force acting above a reference point creates a moment. The calculator uses design force times centerline height plus mount eccentricity. Use the correct reference for the support component being checked.
10. Can I combine different antenna models in one calculation?
Not accurately with one projected-area field. Calculate each model or orientation separately. Then combine loads using the governing structural method and applicable load combinations.
11. Does a passing result approve installation?
No. A passing comparison only means the entered force did not exceed an entered limit. Final approval requires verified product data, governing design loads, connection checks, and qualified engineering review.