2.2 Transmitter Power Limits: Peak Envelope Power (PEP) & Carrier Rules
Key Takeaways
Schedule 2 uses 10 W peak envelope power for Foundation in every Table A row.
For Standard, J3E and R3E use 100 W peak envelope power. C3F also uses 100 W peak envelope power in the 50–52 MHz row. Other cases use 30 W mean power.
For Advanced, most Table C rows use 400 W peak envelope power for C3F, J3E or R3E and 120 W mean power in other cases.
The two lowest Advanced bands use separate limits of 1 W and 5 W peak envelope power expressed as EIRP.
Check bandwidth, power spectral density, exposure and interference requirements separately from the maximum power.
Read the units as part of the limit
In Schedule 2 of the Amateur Class Licence, the power entry depends on the qualification, frequency and sometimes the emission designator. The Radiocommunications (Interpretation) Determination 2025 uses the International Telecommunication Union (ITU) Radio Regulations definitions for the power symbols.
| Symbol | Quantity | How to recognise it |
|---|---|---|
| pX | Peak envelope power (PEP) | At the crest of the modulation envelope, average the transmitter power delivered to the antenna line over one radiofrequency cycle. |
| pY | Mean power | Average the power delivered to the antenna line over a period long in relation to the slowest modulation frequency. |
| pZ | Carrier power | Average the power delivered to the antenna line over a radiofrequency cycle with modulation absent. |
Peak envelope power uses an average over a very short interval at the envelope crest. Mean power uses a longer interval. A constant-envelope frequency-modulated signal can have the same numerical mean and carrier power under steady conditions, but the legal quantity in the relevant Standard or Advanced row is mean power. On amplitude-modulated signals or keyed transmissions, the relationship between average and peak readings depends on the waveform.
Select the row and emission designator
| Schedule 2 row | Higher or special power entry | Other emission cases in that row |
|---|---|---|
| Foundation, Table A items 1–4 | 10 W pX for all emissions | Same limit |
| Standard, Table B items 1–3 and 5 | 100 W pX for J3E and R3E | 30 W pY |
| Standard, Table B item 4, 50–52 MHz | 100 W pX for C3F, J3E and R3E | 30 W pY |
| Advanced, Table C item 1, 135.7–137.8 kHz | 1 W pX EIRP | Same limit |
| Advanced, Table C item 2, 472–479 kHz | 5 W pX EIRP | Same limit |
| Advanced, Table C items 3–9 | 400 W pX for C3F, J3E and R3E | 120 W pY |
A Standard station using frequency modulation for voice (F3E) on 146 MHz uses Table B item 5. F3E is in the other-emission category, so the limit is 30 W pY. At the same frequency a Standard station using J3E voice has a 100 W pX ceiling. A single-sideband data emission with a different final designator, such as J2D, stays in the other-emission category. Identify the full emission code even when two transmissions use the same transceiver setting.
An Advanced station using J3E at 14.200 MHz selects Table C item 3. The power limit in that row for J3E is 400 W pX. The equipment's maximum advertised output does not set the operating limit. If an external amplifier is used, account for its actual RF output into the antenna transmission line. Pick a measurement method suited to the quantity. A steady reading on an average power meter alone cannot establish the peak envelope power of a variable signal.
Worked example: a peak EIRP limit
Equivalent isotropically radiated power (EIRP) expresses antenna input power multiplied by the antenna gain, relative to an isotropic antenna, in the direction being considered. Account for feedline loss before applying gain. Use a linear gain factor when multiplying powers in watts.
Suppose an Advanced operator at 136.0 kHz supplies 20 W pX to a transmission line that delivers half of the power to the antenna, and the antenna's maximum gain relative to an isotropic antenna is 0.08 as a linear factor. The antenna receives 10 W pX. Its maximum EIRP is:
That is below the 1 W pX EIRP ceiling in Table C item 1. A necessary bandwidth above 2.1 kHz would still fail that item's bandwidth condition. Table C item 2 instead uses 5 W pX EIRP and a 3 kHz necessary-bandwidth limit. Keep the frequency, power quantity and antenna assumptions explicit.
Apply the remaining checks
Power limits are ceilings. Using enough power for the contact while avoiding unnecessary interference is good operating practice. ACMA specifically advises minimum power for on-air test transmissions. The general class licence conditions include the Schedule 2 ceilings, section 15 on interference and spurious emissions and section 16 on electromagnetic energy exposure. If a proposed setup has a bandwidth-dependent power-density limit, check that as well as the total power ceiling.
What power limit does Schedule 2 set for a Standard class-licensed station using F3E on 146 MHz?
100 W peak envelope power.
50 W carrier power.
10 W peak envelope power.
30 W mean power.
How is peak envelope power (pX) determined for a radio transmitter?
Average the power delivered to the antenna line over one radiofrequency cycle at the envelope crest.
Measure the direct-current power drawn from the supply.
Average the unmodulated carrier over at least ten minutes.
Multiply the instantaneous voltage peak by the antenna impedance.
What power limit does Schedule 2 specify for an Advanced class-licensed station using J3E at 14.200 MHz?
100 W peak envelope power.
400 W peak envelope power.
1,000 W peak envelope power.
120 W mean power.
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