Microwave link planning tools
Point to point link design from the first clearance check to a full path on terrain: Fresnel zones, the link budget, rain fade and availability.
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How the design is done
A point to point microwave link looks simple on paper: two sites, a clear line of sight, a frequency and an antenna at each end. Getting from there to a link that meets its availability target means accounting for terrain, Fresnel zone clearance, atmospheric absorption, rain, multipath fading and the links already licensed around you. Skip one and the link either underperforms on the day or fails coordination at licensing.
Clearance comes first. Radio energy travels as an ellipsoid around the direct ray, not a pencil beam, and industry practice keeps at least 60 per cent of the first Fresnel zone clear of obstructions. Refraction bends the path, so clearance is checked at an effective earth radius factor k, with the earth bulge between the two ends added to the terrain.
Then the budget. Free space path loss is the floor every other loss sits on, and fade margin is the reserve that rides out the rest. On long paths below about 10 GHz multipath fading usually sets that margin; above that, rain takes over, and the ITU-R chain of rain rate, specific attenuation and path scaling turns a rain climate into an attenuation you can design against.
The tools below start with the quick checks you can run from a site survey and finish with the full path design on terrain.
The workflow, one tool per step
Check the path is clear
Line of sight is not enough. The calculator gives the first, second and third Fresnel zone radii along the path, checks each obstacle against the 60 per cent first zone rule, and adds the earth bulge at the k factor you choose.
Fresnel Zone Calculator FreeBudget the link
Account for every dB between the transmitter and the receiver: EIRP, path loss, received power, noise floor, carrier to noise and fade margin, with presets for microwave, land mobile, WiFi, LTE and satellite links.
Link Budget Calculator FreeSize the rain margin
At the higher microwave bands rain sets the fade margin. The calculator shows each step of the ITU-R chain (P.838 specific attenuation, P.530 path scaling, P.840 cloud and P.676 gases) with a Bureau of Meteorology site lookup for Australian paths.
Rain Fade Calculator FreeDesign the path on terrain
Build the link on a terrain profile and run it to ITU-R P.530-19: Fresnel clearance on the real ground, rain, gas, cloud and multipath fading, adaptive modulation and diversity, antenna patterns and availability, with the provenance of every number. It also plans point to multipoint sectors with a budget per subscriber.
Link Planner Pro
Availability figures are statistical predictions from ITU-R climate data. Confirm the path with a site survey before committing to hardware.
More microwave link planning tools
Often used alongside
Further reading
- What Is Free Space Path Loss (FSPL)? Formula, Examples and the 6 dB Rule FSPL is what a signal loses simply by spreading out as it travels. The formula in every useful form, why it depends on frequency, and where the 6 dB rule fits.
- What Is Radio Line of Sight? Earth Curvature, K-Factor and the Radio Horizon Radio line of sight reaches past what the eye can see. Why a k-factor of 4/3 models atmospheric bending, plus the radio horizon and earth curvature formulas.
- What Is Rain Fade? ITU-R P.838, Rain Zones and Designing for Link Availability Above about 10 GHz, rain decides whether a link survives a downpour. The ITU-R P.838 specific attenuation formula, rain zones, and designing for availability.
- What Is Fade Margin and How Much Do You Need? Fade margin is the decibels your received signal sits above the receiver threshold. The formula, a worked example, and how margin maps to link availability.
- How to Calculate an RF Link Budget: A Step by Step Guide with a Worked Example Add every gain, subtract every loss, then compare against receiver sensitivity. The formula, an at a glance table and a worked 5.8 GHz point to point example.
- Path Loss, Fresnel Zones, and the 80% Rule: A Field Engineer's Refresher Free space path loss, the log distance model, Fresnel zones and two ray ground reflection: the four numbers to be able to estimate before you climb a tower.