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RF Field Guide · propagation additions

See what the air and rain add to a path

Separate clear-air gaseous attenuation from a rain-rate scenario you choose. These losses add to spreading, terrain, and equipment effects; they do not replace them.

Question

For this frequency and path length, how much additional loss comes from standard-condition atmospheric gases, and how much comes from the selected rain rate?

Inputs

Choose the path
Direct distance

This model does not calculate availability. Choosing a target returns an explicit unsupported-model message instead of guessing climate statistics.

Answer

Enter a path, frequency, polarization, and point rain rate to separate the two modeled contributions.

Working

Calculate to see the formulas.

Visual explanation

Calculate to see the path view.

Interpretation

Calculate a scenario to compare which layer is larger for these inputs.

Limitations

Assumptions, model bounds, and excluded effects
Model identity
Gaseous loss uses WISP Planner's standard-condition terrestrial approximation, not the ITU-R P.676 line-by-line method. Rain specific attenuation uses ITU-R P.838 coefficients, followed by WISP Planner's stated effective-path approximation.
Three different planning results
A nominal result uses the stated standard-condition model. A manual weather scenario applies the rain rate entered here. Reliability needs location-specific rain statistics from ITU-R P.837 and the terrestrial-link method in ITU-R P.530; this lesson does not calculate it.
High-band path qualification
At 10 GHz and above, establish clear line of sight and Fresnel clearance before assessing weather reliability. A reliability model cannot make an obstructed path acceptable.
Other weather mechanisms
ITU-R P.839 covers rain-height and wet-snow context; ITU-R P.841 covers cloud and fog attenuation. Neither is calculated by this lesson.
Scenario, not forecast
The rain rate is supplied by you. WISP Planner does not fetch weather, infer local climate, or predict when this rain rate will occur.
No availability claim
This surface does not turn a point rain rate into uptime, outage probability, fade margin, or a service-level promise.
No compliance claim
The result does not determine jurisdictional, licensing, engineering, or safety compliance.
Model bounds
The combined public calculation supports 1–100 GHz and paths greater than 0 through 500 km. Rain rate must be positive. Only horizontal and vertical linear polarization are modeled.
Excluded effects
Free-space spreading, terrain, diffraction, vegetation, buildings, antenna patterns and alignment, equipment losses, interference, noise, and receiver performance remain separate.

Next step

Calculate a scenario, then continue with the free-space and link-budget lessons to build the full signal chain.