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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.

The place: River and flood plain

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.