Antennas — Tool
Beam coverage animator
A horn's beam isn't one shape — it breathes across the band, and it's rarely round. This tool animates the 3 dB beam cross-section from real manufacturer data (E-plane sets the height, H-plane the width), then answers the planning question: over your sweep, what's the worst-case beamwidth, and how much of the target does that actually illuminate at your distance?
Inputs
Reading the result
The oval is the beam's −3 dB contour: inside it the field is within half power of boresight; outside, it falls away fast. The worst-case beamwidth is the smallest of the E- and H-plane values anywhere in your sweep — the frequency where the beam is tightest is the frequency that decides your setup, because every point on the target must be covered at every frequency of the test.
Coverage converts that angle to metres on a flat target: coverage = 2 · d · tan(θ/2). Try the 3115 across its full 0.75–18 GHz band at 1 m — the answer is a strip barely 16 cm wide, set by the top end of the band where the beam is narrowest. That's why RS103 setups over wide bands need multiple antenna positions or a band split, and why "the antenna covers the EUT" is a claim that has to be checked per band, not per test.
Curve data is digitised from manufacturer half-power beamwidth plots to about ±2°. It represents typical performance — a specific serial number, mounting arrangement and site will differ. Verify coverage for formal work against your antenna's calibration data and the applicable standard.
Antenna library: ETS-Lindgren 3115, 3117, 3106, 3106B, 3144 LPDA, plus one unnamed 1–2 GHz horn awaiting identification. Mind the 3106 vs 3106B distinction — they are different antennas. More are added as plots are digitised.