2.3 Permitted Emissions, Modulation Modes & Bandwidth Restrictions
Key Takeaways
The class licence uses ITU Radio Regulations Appendix 1 (Rev. WRC-19) to determine the emission designation.
The three emission symbols describe main-carrier modulation, the modulating signal and the information conveyed.
A full emission designator includes four characters for necessary bandwidth, such as 2K80 in 2K80J3E.
Schedule 2 distinguishes hard necessary-bandwidth ceilings from rows that impose a power spectral density cap above a threshold.
Bandwidth, spurious emissions and harmful interference are separate checks. Voluntary band plans help coordinate modes within lawful privileges.
Read the emission designator
Under section 5(2) of the Amateur Class Licence, work out the emission designation using International Telecommunication Union (ITU) Radio Regulations Appendix 1 (Rev. WRC-19). The three classification symbols tell you what the transmitter does to the carrier, the kind of signal that modulates it and the information sent. A complete designation also includes four characters at the front to specify necessary bandwidth, the bandwidth sufficient to carry the information at the required rate and quality under stated conditions.
| Position | What it identifies | Useful examples |
|---|---|---|
| First symbol | Modulation of the main carrier | A double-sideband amplitude modulation; J suppressed-carrier single sideband; R reduced or variable-carrier single sideband; F frequency modulation; G phase modulation; C vestigial sideband; N unmodulated |
| Second symbol | Nature of the modulating signal | 0 no modulating signal; 1 one digital channel without a modulating subcarrier; 2 one digital channel with a modulating subcarrier; 3 one analogue channel |
| Third symbol | Information sent | A aural telegraphy; B machine-received telegraphy; D data, telemetry or telecommand; E telephony; F television; N no information |
For example, J3E is suppressed-carrier single-sideband voice, and F3E is frequency-modulated analogue voice. A1A describes aural Morse sent by keying the carrier. J2D describes single-sideband digital data carried via a modulating subcarrier. C3F describes analogue vestigial-sideband television. The actual modulation and information determine the designator. A name shown in a transceiver menu by itself does not settle it.
ACMA gives 2K80J3E as an example of J3E with a necessary bandwidth of 2.80 kHz, and 16K0F3E as an FM voice example with a necessary bandwidth of 16.0 kHz. Those example widths are ways to describe emissions. For the operating limit, find the appropriate row of Schedule 2.
Interpret column 3 of Schedule 2
Occupied bandwidth is a separate measure based on the distribution of mean power in the actual emission. Schedule 2 column 3 generally specifies limits using necessary bandwidth. Look for the kind of condition stated in the row.
| Schedule 2 location | Applicable condition |
|---|---|
| 7.100–7.300 MHz for all three tiers; also 3.776–3.800 MHz and 10.100–10.150 MHz for Advanced | Necessary bandwidth must be at most 8 kHz. |
| Items A1, B1 and C3, including 7.000–7.100 MHz | If necessary bandwidth exceeds 8 kHz, maximum power spectral density must be at most 1 W per 100 kHz. |
| 28.000–29.700 MHz for all three tiers | The same 1 W per 100 kHz power-density cap applies when necessary bandwidth exceeds 16 kHz. |
| 50.000–52.000 MHz for Standard and Advanced | Necessary bandwidth must be at most 100 kHz. |
| 135.7–137.8 kHz and 472–479 kHz for Advanced | Necessary bandwidth must be at most 2.1 kHz and 3 kHz respectively. |
| A row marked “No limitation” in column 3 | There is no additional limitation in that column. Column 2 and the other applicable conditions still apply. |
A hard bandwidth ceiling applies even at very low power. A power spectral density cap limits the power relative to bandwidth when the threshold is crossed. The legal wording refers to maximum power spectral density. Measuring total output power alone cannot show that a non-uniform emission meets that cap.
Worked comparison on either side of 7.100 MHz
A Standard operator proposes an experimental emission with 9 kHz necessary bandwidth and sufficient margin from the row edges. At 7.150 MHz, Table B item 2 imposes an 8 kHz ceiling, so the proposal fails the bandwidth condition. At 7.050 MHz, Table B item 1 instead triggers the 1 W per 100 kHz maximum spectral-density rule above 8 kHz. At 7.050 MHz the operator must check that rule, the power limit for the emission and the other operating conditions before transmitting. Using the same 9 kHz signal at a different frequency changes which rule applies.
Keep the wanted and unwanted emissions in view
A voluntary band plan may recommend narrower signals within a particular activity segment. Following the convention reduces interference among amateurs. Section 15 separately addresses harmful interference and spurious emissions. Excessive drive and clipping can produce unwanted emissions, so check actual spectral performance when changing levels or equipment. The class licence's spurious-emission limits and Schedule 2 bandwidth conditions serve different purposes. A transmitter producing the right designator at a permitted frequency can still breach another condition.
What does the emission designator J3E identify?
Double-sideband amplitude-modulated telephony.
Frequency-modulated voice.
Suppressed-carrier single-sideband telephony.
Frequency-shift keyed data.
A Standard station proposes a 9 kHz necessary-bandwidth emission at 7.150 MHz. What does Schedule 2 require?
It is permitted whenever total mean power is below 30 W.
It is permitted when the maximum spectral density is below 1 W per 100 kHz.
It is permitted when the band plan allows the activity.
It exceeds the hard 8 kHz necessary-bandwidth ceiling in the applicable row.
In the ACMA example 2K80J3E, what does 2K80 describe?
A necessary bandwidth of 2.80 kHz.
A transmitter output of 2.80 W.
The frequency of a repeater offset.
A measured carrier suppression of 2.80 dB.
Sections you finish are checked off in the contents.