Test Environment & Equipment

Test Environment

Radiated emission measurements are performed inside shielded facilities to eliminate external RF interference. Module 04 covered the three common environments used for RE compliance testing in depth (illustrated views of each are there); the quick reference below is just for orientation:

What Module 04 did not cover is exactly how the Equipment Under Test (EUT) is positioned once it is inside one of these environments. The EUT is placed on a non-conductive table positioned above a ground plane. Measurements are then taken while rotating the EUT through 360° and varying the antenna height, so that the worst-case orientation and elevation angle — the one producing the maximum emission level — is never missed.

EUT Test Setup Diagram (Animated)

The EUT sits on a non-conductive table above the ground plane. Watch the turntable rotate the EUT through 360° while the antenna sweeps height on its mast — the receiver logs the maximum reading found across every combination, and the radiating field lines pulse to show the measurement actively in progress.

How Each Antenna Type Works

Every antenna in the signal chain is built to be maximally sensitive to a specific frequency range and field type. The four animated diagrams below show the physical mechanism each one relies on.

Biconical Antenna (30–300 MHz, E-field)

Two cone-shaped elements act as a wideband dipole — the cone shape (rather than a thin rod) broadens the antenna's usable bandwidth by presenting a more gradual impedance transition across frequency.

Log Periodic Antenna (200 MHz–1 GHz, E-field)

A series of progressively shorter dipole elements, each resonant at a different frequency within the band. As frequency changes, the "active region" of the antenna that's actually radiating shifts smoothly along the boom — watch the glowing element move as the sweep frequency changes.

Horn Antenna (>1 GHz, E-field)

A flared waveguide that gradually expands the electromagnetic wave from a narrow guided mode to free space, concentrating gain into a narrow, highly directional beam — essential at short wavelengths where a wide beam would waste energy in directions the receiver doesn't care about.

Loop Antenna (9 kHz–30 MHz, H-field)

A simple conductive loop couples directly to the magnetic (H) field rather than the electric field — a changing magnetic field through the loop induces a current in it (Faraday's law), which is exactly the near-field coupling mechanism Module 04 described for magnetic field testing.

Typical Test Equipment

A full RE test setup is a signal chain from the radiating EUT to a calibrated reading on the receiver, plus the mechanical and support equipment that makes repeatable measurement possible.

Signal Chain (Antenna → LNA → Cables → Receiver/Analyzer)

Mechanical

Support

Interactive: Antenna Factor vs. Frequency

Every antenna has a calibrated Antenna Factor (AF, dB/m) that converts the voltage measured at its output back into the true field strength at the EUT: Field (dBµV/m) = Receiver Reading (dBµV) + Antenna Factor (dB/m). Hover to see how AF varies by frequency and antenna type — this is exactly the kind of calibration curve that ships with every real antenna's cal certificate.

Interactive: Signal Chain Gain/Loss Budget

The net correction applied to a raw receiver reading is the sum of every stage in the signal chain: antenna factor (a loss, effectively), cable loss (a loss), and LNA gain (a gain). Toggle traces in the legend to see how removing the LNA would shift the whole correction curve.