Rain Fade Calculator

1. Enter your operating frequency and effective rain path length.
2. Use a rain rate based on local exceedance or design targets.
3. Select polarization, then keep auto coefficients or set manual values.
4. Set availability and fade margin to check pass or shortfall.
5. Press Calculate, then export CSV or PDF for your records.

Rain-rate inputs and site exceedance

Use rain rate from local exceedance statistics, not daily averages. In many regions, 0.01% annual exceedance supports high availability, while 0.1% suits standard links. Higher rain rates drive attenuation nonlinearly through exponent α, so confirm units in mm/h. Regional convective storms can exceed published maps, so validate with recent gauge records when available. If data is limited, start conservatively and refine during commissioning.

Frequency sensitivity across common bands

Rain attenuation rises with frequency as wavelength shortens. Links near 6–11 GHz often tolerate heavy showers with modest margin, while 18–23 GHz and 24–38 GHz can see deep fades. Polarization matters: horizontal typically produces slightly higher attenuation than vertical. At higher bands, consider larger antennas and shorter hops to preserve fade margin during monsoon peaks. This calculator auto-estimates k and α so band choices compare consistently.

Path length, reduction effects, and planning

Total attenuation depends on distance through rain, but rainfall is rarely uniform along the full route. The effective-path factor reduces the full length using a practical term based on L, γ, and frequency. For long paths, the reduction prevents unrealistic linear growth, yet attenuation can still exceed budgets. Shortening the hop or adding a relay often beats increasing transmit power.

Margin checks and availability targets

Fade margin is the extra budget remaining after clear-sky losses. After calculating attenuation, the tool compares it to your margin and flags a shortfall. Availability settings provide a planning adjustment: higher availability implies a tougher attenuation case. For compliance, align rain rate selection and availability practice with your standard.

Reporting, audits, and repeatable comparisons

Exportable outputs document engineering decisions. CSV is useful for spreadsheets and batch comparisons, while PDF provides a quick result sheet for reviews. Use the history panel to track scenarios such as antenna size, hop splits, or polarization choices. When updating a design, rerun inputs to confirm new rain data has not shifted risk. Store exports with project IDs.

Q: What does the calculator estimate?

A: It estimates rain attenuation using specific attenuation, an effective path factor, and a planning adjustment for your availability target. Use it for quick link-budget checks and scenario comparisons.

Q: Which rain rate should I enter?

A: Enter a design rain rate in mm/h from local exceedance statistics or your project standard. Avoid using monthly averages, because short intense events usually drive worst-case attenuation.

Q: When should I use manual k and α?

A: Use manual values when your organization specifies coefficients for certain bands or climates, or when you have validated parameters from measured performance. Auto mode is useful for early feasibility studies.

Q: How do I interpret “margin left”?

A: Margin left equals fade margin minus the estimated attenuation for your availability setting. A positive value indicates remaining buffer; a negative value indicates a shortfall that may require design changes.

Q: How can I reduce rain-fade risk?

A: Reduce path length, choose a lower frequency band, increase antenna gain, improve alignment, or add diversity. In many cases, splitting a long hop into two shorter hops gives the largest benefit.

Q: Do exports include my history table?

A: Exports include the latest calculated result summary only. Use the on-page history list for quick review, and repeat downloads after each scenario if you need multiple records for a report.