Result preview
Enter your path values and submit the calculator to view received power, link margin, EIRP, path loss, clearance guidance, and a distance chart.
Calculator Inputs
Example Data Table
| Parameter | Example Value | Unit | Purpose |
|---|---|---|---|
| Frequency | 18.0 | GHz | Operating band for the microwave hop. |
| Distance | 12.0 | km | Total radio path length between sites. |
| TX Power | 23.0 | dBm | Output level from the transmitter radio. |
| TX / RX Antenna Gain | 34.0 / 34.0 | dBi | Directional amplification from both antennas. |
| Combined Extra Losses | 6.7 | dB | Rain, atmospheric, and miscellaneous attenuation. |
| Receiver Sensitivity | -74.0 | dBm | Minimum acceptable receive level for the service. |
Formula Used
Free Space Path Loss: FSPL (dB) = 92.45 + 20 log10(distance in km) + 20 log10(frequency in GHz)
EIRP: EIRP (dBm) = TX Power - TX Feeder Loss + TX Antenna Gain
Received Power: RX Power (dBm) = TX Power - TX Feeder Loss + TX Antenna Gain - FSPL - Rain Fade - Atmospheric Loss - Misc Loss + RX Antenna Gain - RX Feeder Loss
Link Margin: Link Margin (dB) = Received Power - Receiver Sensitivity
Excess Margin: Excess Margin (dB) = Link Margin - Target Fade Margin
Midpoint Fresnel Radius: F1 midpoint (m) = 8.657 × sqrt(distance in km ÷ frequency in GHz)
Recommended Clearance: Clearance (m) = 60% of the midpoint first Fresnel radius
How to Use This Calculator
- Enter the operating frequency and total path distance.
- Fill in transmitter power, feeder losses, and both antenna gains.
- Add environmental and implementation losses such as rain or miscellaneous penalties.
- Provide receiver sensitivity and the target fade margin for your design goal.
- Press the calculate button to display received power, link margin, and a status summary.
- Review Fresnel clearance guidance and the chart to understand distance effects.
- Download the result as CSV or save the report as PDF for documentation.
Frequently Asked Questions
1. What does a microwave link budget measure?
It estimates whether a radio path can deliver enough signal at the receiver after accounting for distance, antenna gains, feeder losses, and environmental attenuation.
2. Why is fade margin important?
Fade margin is the reserve above receiver sensitivity. It helps the link survive rain, multipath fading, and short-term signal drops without service interruption.
3. What is EIRP in this report?
EIRP is the effective isotropic radiated power. It combines transmitter output, feeder loss, and antenna gain into one value that describes radiated strength.
4. Does this calculator replace a detailed path study?
No. It is a planning tool. Final engineering should also check terrain, Fresnel obstruction, licensing limits, polarization, availability targets, and equipment-specific thresholds.
5. Why does the chart worsen with longer distance?
Path loss rises logarithmically with distance. As the hop gets longer, received power drops and link margin shrinks unless you improve gains, power, or losses.
6. What losses should go into miscellaneous loss?
Use it for implementation penalties not listed elsewhere, such as connector loss, branching loss, radome penalty, alignment tolerance, or extra design allowances.
7. How should I choose receiver sensitivity?
Use the value from the actual radio and modulation setting. Different channel widths, coding rates, and modulation schemes can change sensitivity significantly.
8. What does recommended Fresnel clearance mean?
It is a midpoint guide showing how much of the first Fresnel zone should remain clear. Obstructions can cause diffraction loss and weaken reliability.