Calculator Inputs
Example Data Table
| Distance (km) | Freq (GHz) | Tx Power (dBm) | Tx/Rx Gain (dBi) | Losses (dB) | Sensitivity (dBm) | Fade Target (dB) | Expected Result |
|---|---|---|---|---|---|---|---|
| 2.500 | 5.800 | 23.00 | 8 / 8 | Tx 1.0, Rx 1.0, Extra 2.0 | -90.0 | 15.0 | Good margin when clear LOS exists. |
Use this as a starting point, then tune losses and fade margin for your environment.
Calculation History
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Formula Used
- Free-space path loss (FSPL): FSPL(dB) = 92.45 + 20·log10(dkm) + 20·log10(fGHz).
- EIRP: EIRP(dBm) = Ptx(dBm) + Gtx(dBi) − Ltx(dB).
- Received power: Prx = EIRP + Grx − Lrx − FSPL − Lextra.
- Link margin: Margin(dB) = Prx(dBm) − Sensitivity(dBm).
- Max distance at target fade margin: solved by rearranging FSPL using the fade target.
- Radio horizon LOS estimate: d(km) ≈ 3.57·(√h1 + √h2), heights in meters.
- First Fresnel zone (midpoint): r(m) ≈ 8.66·√(dkm/fGHz), with 60% recommended clearance.
- Propagation delay: t(ms) = (d(m)/c)·1000, where c ≈ 299,792,458 m/s.
How to Use This Calculator
- Enter your planned distance and frequency for the backhaul hop.
- Fill in Tx power, antenna gains, and estimated cable/connector losses.
- Set receiver sensitivity for your required data-rate and modulation.
- Choose a fade margin target that matches reliability expectations.
- Provide drone and ground heights to check the LOS horizon estimate.
- Add midpoint obstacle clearance to verify Fresnel clearance, if known.
- Click Calculate to see results under the header.
- Download CSV or PDF to attach to method statements and permits.
Note: This is a planning tool. Always validate with a site survey, spectrum scan, and safety procedures.
Professional Notes for Drone Backhaul Planning
1) Purpose and scope
Construction drones often depend on a stable backhaul hop to stream video, upload progress imagery, and relay telemetry. This calculator estimates a first‑pass radio link budget using free‑space path loss, antenna gains, and practical loss terms. It is intended for rapid feasibility checks during planning, not as a substitute for a detailed RF survey.
2) Inputs that drive reliability
Distance and frequency set the basic attenuation. Transmit power and antenna gains raise effective radiated power, while cable and connector losses reduce it. Receiver sensitivity should match the modulation and data‑rate you require. Add “additional losses” for foliage, temporary obstructions, rain fade, polarization mismatch, or imperfect alignment.
3) Reading margin and pass or fail
Received power is compared to sensitivity to produce link margin. A positive margin is not the goal by itself; the target is a margin that exceeds your required fade value. Fade margin helps protect against swings caused by crane movements, multipath, dust, changing humidity, and intermittent obstructions.
4) Line of sight and Fresnel clearance
Even when a link budget looks strong, geometry can break the path. The line‑of‑sight horizon estimate uses drone and ground heights to flag obvious range issues. The midpoint Fresnel radius estimate helps you judge whether scaffolding, stockpiles, or temporary structures intrude into the recommended clearance zone.
5) Field workflow for construction teams
Use the example values, then adjust inputs to match actual radios and antennas. Plan the hop location, mast height, and drone operating altitude. If the calculator reports a narrow margin, consider higher gain antennas, reduced distance, improved mounting height, or a lower throughput mode. Document results using CSV or PDF for method statements and shift handovers.
FAQs
1) What distance should I enter?
Enter the straight‑line hop distance between the drone and the ground station or relay point. If the route bends around structures, model the longest clear segment or plan a relay to keep each hop short.
2) How do I choose receiver sensitivity?
Use the sensitivity published for the specific data‑rate or modulation you plan to run. Higher throughput usually needs stronger signal, so the sensitivity value will be less negative.
3) What is a reasonable fade margin?
For busy sites, 10–25 dB is common depending on criticality. Increase the target for safety‑critical video or command links, and for environments with frequent partial obstructions.
4) Why does the LOS check matter if margin is high?
Non‑line‑of‑sight paths can collapse suddenly with small movements. The LOS check is a fast warning that earth curvature and low heights may block the path before your link budget assumptions apply.
5) What should I put in additional losses?
Start with 1–3 dB for connectors and alignment uncertainty, then add site‑specific penalties for foliage, dust, weather, or known obstructions. Calibrate this term after a short on‑site test.
6) How is Fresnel clearance used here?
The calculator estimates first‑zone radius at the midpoint and recommends 60% clearance. If you can estimate obstacle clearance at midpoint, it flags whether that clearance meets the recommendation.
7) Can I use this for mesh relays or multi-hop links?
Yes. Run one hop at a time and keep consistent sensitivity and fade targets. Compare results across candidate relay placements, then choose the layout that provides the best margins and clear geometry.