Antenna Downtilt Calculator (Labs)

How to use this page

Enter the antenna height, receiver height and the datasheet's half-power vertical beamwidth to see where the beam meets the receiver plane, or enter a distance to find the required tilt. The result is a flat-earth planning figure with a clearly labelled 4/3-earth check.

Read the full guide (opens in a new tab)

Where an antenna’s vertical beam meets the receiver plane for a given height, beamwidth and tilt — or the tilt that puts it at a chosen distance. Distances drawn to scale, heights exaggerated. Flat earth, one vertical cut.

The question

Tilt

Positive is downtilt. A negative value is uptilt and is reported as such. Or drag the red handle in the side view.

Tilt type

Electrical tilt on an azimuth-symmetric antenna lowers the beam in every direction; mechanical tilt lowers it along the boresight only. The plan view draws the difference.

Antenna and site

Antenna height above ground

Radiation centre, not the top of the mast.

Receiver height above its ground

1.5 m for a mobile or handheld. 0 reads the ground itself.

Vertical beamwidth, half-power (−3 dB)

The figure from the antenna’s datasheet, for the vertical cut you are aiming along. Not filled in from the catalogue — published figures are not consistent enough to compute against.

Ground elevations if the site and the target sit at different heights

Site ground elevation

Leave at 0 if unknown; only the difference from the target matters. Use the same vertical datum for both elevations.

Target ground elevation

Same as the site (flat ground)

This calculator needs JavaScript. The geometry and the drawings are computed in the browser, so with scripting off the fields above do nothing. The basis and the limits below apply to every figure this page produces, and the formula is Δh ÷ tan α: the antenna’s height above the receiver plane divided by the tangent of the angle below horizontal, with the half-power edges at half the beamwidth either side of the tilt.

Enter the vertical beamwidth from the antenna’s datasheet to see where the beam lands.

Basis: half-power (−3 dB) vertical beamwidth, entered by you, assumed symmetric about the beam centre in the vertical cut you are aiming along. The edges shown are where the pattern is half its peak power — Telewave engineering’s working convention, pending confirmation. A beamwidth quoted to another reference (−10 dB, first null) will not be read correctly here.

What this is, and is not

−3 dB is not the edge of coverage. The half-power edges are pattern points, not a coverage boundary. Reception can exist outside these distances and can fail within them — coverage depends on the link budget, terrain and the receiver, none of which this page knows. For a range estimate use the Coverage Calculator, and read the two side by side as different questions.

Flat earth, no terrain. Flat earth between the antenna and the target, no terrain, no obstructions. A 4/3-earth check is used only to say where this flat-earth reading stops applying and roughly how far it understates — not to compute where the beam lands on a curved earth. Height above average terrain (HAAT) from the Coverage Calculator’s terrain estimate is an average over 3–16 km radials; it is not the height above the particular ground you are aiming at, and it is not FCC HAAT.

One vertical cut. These figures are for one vertical cut through the pattern — the direction you are aiming along — and assume the beam is lowered by the stated tilt in that cut. With electrical downtilt on an azimuth-symmetric antenna that holds in every direction; a mechanically tilted panel is lowered by the stated angle only along its boresight.