5.1 Electromagnetic Compatibility (EMC) & Equipment Immunity Standards
Key Takeaways
EMC concerns unwanted disturbance and immunity to disturbance. EME exposure limits concern people who may be exposed to the RF field.
A report coinciding with a transmission suggests a possible source. Inspect the emission and how RF reaches the affected equipment before drawing a compliance conclusion.
Class Licence Schedule 1 applies general public reference levels in publicly accessible places and gives separate low-risk and higher-risk assessment paths.
Use antenna access, average total power, height and average EIRP as specified in Schedule 1. A qualification or transmitter PEP alone cannot establish the assessment path.
Trace the interference
Electromagnetic compatibility (EMC) means that equipment can function in its electromagnetic environment while keeping its disturbance to other equipment within acceptable levels. Emission describes what leaves the source. Immunity describes how well a device operates when it is exposed to a disturbance. Disturbance can reach equipment by radiation or along a conductor.
Suppose a neighbour hears speech from their powered speakers when your HF transmitter is keyed. Check the timing, frequency and repeatability. An external speaker lead could pick up the wanted RF signal and the amplifier could rectify it into audible speech. A harmonic or other unwanted emission could also be involved. The symptom alone does not establish which signal or path is responsible or whether equipment complies. ACMA can investigate compliance with rules that apply to the device or its supplier. The operator separately checks applicable station conditions, including Class Licence section 15.
| Evidence | Practical check |
|---|---|
| Speech is strongest with a particular lead connected | With permission, reposition the lead or try an appropriate clip-on ferrite to investigate common-mode pickup. |
| Noise appears at multiples of the station frequency | Measure the transmitter into an appropriate test load with a suitable attenuator. Check filtering and whether the transmitter or amplifier is overloaded. |
| Noise on the station receiver changes when a local appliance switches | Isolate the source by testing one accessible device at a time. Preserve the electrical protective earth. |
A ferrite choke appropriate to the frequency can impede RF current flowing on the outside of a coaxial shield. A transmitter low-pass filter can suppress harmonics above its passband. Choose a measure that matches the observed coupling. ACMA’s supplier rules cover applicable product standards and compliance labelling, including the Regulatory Compliance Mark where required. Station operation still has its own interference and exposure conditions.
Check exposure to people
Electromagnetic energy (EME) exposure is a separate check. Class Licence section 16 gives effect to Schedule 1. Clause 2 applies ARPANSA’s general public reference levels to places accessible to members of the general public and addresses simultaneous transmissions on multiple frequencies. Consider accessible places such as a walkway, balcony or garden, including on your own property. An amateur qualification alone does not establish the controlled exposure classifications defined in the standard.
For a non-mobile station, Schedule 1 clause 3(1) gives two low-risk paths. The first requires average total power to all antennas of at most 100 W, with every antenna inaccessible to members of the general public. The second requires the base of the lowest antenna to be at least 10 m above ground and average total EIRP of all antennas at most 3,200 W in any direction. A mobile station qualifies under clause 3(2) if average total power to all antennas is at most 100 W. Clause 3 also describes when qualifying measurements or calculations and their documentation support a rebuttable presumption. Clause 2 still applies.
Worked example. A new fixed station feeds 75 W average to a single antenna that a member of the general public can touch. The antenna base is 4 m above ground. The station fails the accessibility condition on the first path and the height condition on the second. Before operation, apply the higher-risk measurement or calculation provisions in clause 4 and hold the clause 6 records, including the declaration, assessment details, results and station configuration. If the configuration changes, recheck the conditions and update the declaration where required. The applicable power for exposure screening is average power, and the test for antenna-fed power differs from the EIRP test.
If the operator raises the antenna so members of the general public cannot reach it and leaves the total at 75 W average, the first non-mobile low-risk path may apply after reassessment. If they subsequently add an amplifier that brings total antenna-fed power above 100 W, recheck both paths. A station falling outside clause 3 after a configuration change is subject to clause 4 from the change. Keep exposure checks current when antenna gain, height or mode changes. When buying or supplying equipment, ACMA’s amateur licensing guidance identifies the separate General Equipment Rules and technical standards, and explains the permit path where required for a non-compliant device.
Amateur Class Licence, Schedule 1 · ARPANSA RPS S-1 · ACMA amateur radio licences · ACMA equipment rules · IEC EMC terminology
An external speaker lead picks up a transmitter’s wanted RF signal, and the speaker amplifier turns it into audible speech. Which mechanism does this evidence support?
A second harmonic generated in the amateur transmitter.
RF coupling into the speaker system and limited immunity to that signal.
Human exposure above the public reference level.
A receiver fault in the amateur transceiver.
A new fixed station feeds 75 W average to one antenna that visitors can reach. The antenna base is 4 m above ground. Which exposure assessment applies?
The 100 W test alone places it within clause 3(1)(a).
The height of 4 m satisfies clause 3(1)(b).
The higher-risk measurement or calculation and record provisions apply.
Only an occupational limit applies because the operator holds an amateur qualification.
A test identifies unwanted RF current on the outside of a coaxial feedline. Which change directly addresses that path?
Fit a suitable common-mode choke on the feedline.
Disconnect the electrical safety earth.
Raise transmitter output to overcome the current.
Move the receiver to a wider filter setting.
Sections you finish are checked off in the contents.