--- title: "Microwave backhaul across a river valley | Nexus Observatory" description: "An 18 GHz hop from the church tower to a mast on the far side of the flood plain: its Fresnel zone F1, clearance over the town and trees…" url: https://observatory.global/environments/networks/backhaul-fresnel/ publisher: Nexus Observatory Inc. updated: 2026-10-29 --- Microwave backhaul across a river valley. A river valley with a town on the north bank. A microwave hop crosses it from the church tower. Layers Scenario A river valley with a town on the north bank. A microwave hop crosses it from the church tower. 01/04 500 MHz 1 GHz 2 GHz 5 GHz 10 GHz 20 GHz 40 GHz 18 GHz fixed links: 17.70–19.70 GHz · λ 16.0 mm · Microwave backhaul · ITU-R F.595 Network scenes # Microwave backhaul across a river valley An 18 GHz hop from the church tower to a mast on the far side of the flood plain: its Fresnel zone F1, clearance over the town and trees, and what a new building in the path costs. [Radio access in a city centre](https://observatory.global/environments/networks/ran-city/) [Open RAN in a suburb](https://observatory.global/environments/networks/oran-suburb/) [AI-RAN at a stadium](https://observatory.global/environments/networks/ai-ran-stadium/) [Private 5G in an open-pit mine](https://observatory.global/environments/networks/private5g-mine/) [Private 5G at a container port](https://observatory.global/environments/networks/private5g-port/) [LoRaWAN across a farm and village](https://observatory.global/environments/networks/iot-farm/) [IoT in the city: a street-light mesh and LoRaWAN](https://observatory.global/environments/networks/iot-city/) [Industrial IoT in a process plant](https://observatory.global/environments/networks/iot-plant/) [Satellite direct to device in a mountain valley](https://observatory.global/environments/networks/ntn-d2d/) [Microwave backhaul across a river valley](https://observatory.global/environments/networks/backhaul-fresnel/) The place: [River and flood plain](https://observatory.global/environments/river-floodplain/) ## In this scene **Dish in the church tower**: A 0.6 m dish behind a louvre in the tower: the highest point in town without a new mast. (ITU-R F.595 (18 GHz arrangement), ITU-R F.699 (antenna pattern)) Scene input: 18 dBm transmit power, −70 dBm threshold **Mast across the flood plain**: The far end of the hop on a lattice mast on the valley side, beyond the levees. (ITU-R P.530-18) ## Computed for this scenario **18 GHz hop**: 1.30 km · 18 GHz **Worst clearance of F1**: 1107 % (clear) **Knife-edge loss (P.526)**: 0.0 dB **Free-space loss (P.525)**: 119.8 dB **Received level**: -24.1 dBm · margin 45.9 dB ## Scenarios **Today**: Fresnel zone F1 clears the roofs and trees. **New building in the path**: A 42 m building is planned beside the river: its roof cuts into the Fresnel zone and adds diffraction loss. ## Tour transcript 1. A river valley with a town on the north bank. A microwave hop crosses it from the church tower. 2. The red ellipsoid is Fresnel zone F1: most of the energy travels inside it. 3. A 42 m building is planned in the path: its roof cuts into the zone, and the knife-edge loss is computed. 4. The far end: a lattice mast beyond the levees. ## How the numbers are computed The profile samples the ground and every drawn roof between the ends. Clearance is measured against the Fresnel radius F1 √(λ d1 d2 / d) with the Earth bulge for k = 4/3 (ITU-R P.530); 60 % of F1 clear counts as unobstructed. The worst point gives a single knife-edge loss J(v) (ITU-R P.526-15 eq. 31). Received level is transmit power plus two 0.6 m dish gains (ITU-R F.699, 60 % efficiency) less free-space (ITU-R P.525) and diffraction loss. © 2026 Nexus Observatory Inc. **Legal** [Privacy notice](https://observatory.global/legal/privacy/) · [Terms of use](https://observatory.global/legal/terms/) · [Cookie policy](https://observatory.global/legal/cookies/) · [Accessibility](https://observatory.global/legal/accessibility/) · [Official languages](https://observatory.global/official-languages/) · [Trademarks](https://observatory.global/trademarks/) · [Notices](https://observatory.global/notices/) **Company** [About](https://observatory.global/about/) · [Stewardship](https://observatory.global/consortium/) · [Contact](https://observatory.global/contact/)