5.3 Spectrum Sharing, Secondary Allocations & Power Choice
Key Takeaways
The Australian allocation table uses capitals for primary services and mixed case for secondary services.
Under Spectrum Plan section 12, secondary services must protect primary services from harmful interference and cannot claim protection from harmful interference caused by them.
Amateur operation on 430–450 MHz is secondary to primary radiolocation in Australia. Check the exact sub-band and applicable footnotes for additional sharing conditions.
Use enough power for a reliable contact. The legal limits are those in the applicable licence, including Schedule 2 for personal class-licensed stations and section 15 on harmful interference.
Read the Australian allocation column
The Australian Radiofrequency Spectrum Plan allocates frequencies to services. Read the Australian table and its footnotes for domestic use. An upper-case service name such as RADIOLOCATION denotes a primary service. Mixed case, such as Amateur, denotes a secondary service.
| Australian band example | What the allocation shows |
|---|---|
| 144–146 and 146–148 MHz | Amateur is primary in both rows. The 144–146 MHz row also lists amateur-satellite as primary. |
| 430–450 MHz | Amateur is secondary and radiolocation is primary. The plan splits this range into several rows with different additional services and footnotes. |
| 10.100–10.150 MHz | Fixed is primary and amateur is secondary. Read Australian footnote AUS57 on radiolocation use as well. |
For 30 metres, the Australian Class Licence lists 10.100–10.150 MHz for Advanced stations in Table C item 4, with an 8 kHz necessary-bandwidth ceiling and the row’s emission-specific power limits. The WIA plan gives narrowband operating recommendations. Apply the legal row and the voluntary recommendations separately.
On 70 centimetres, 432.200 MHz and 445 MHz fall in different Australian allocation rows. Both show primary radiolocation and secondary amateur use. The 432–438 MHz row also lists secondary active Earth exploration-satellite. The 440–450 MHz row lists secondary fixed and mobile. AUS101A designates relevant services principally for defence and national security, and AUS95 permits certain fixed and mobile defence operations provided they do not cause harmful interference to other allocated services in that band. Read the complete footnote before drawing a conclusion about a particular station or frequency.
Allocation status and permission to transmit need separate checks. A primary Australian amateur allocation can still have a local restriction or a competing authorised use. Read the actual station’s class or apparatus conditions and the location. For example, section 18 prevents a class-licensed operator from operating at frequencies and within areas authorised by a spectrum licence. Hearing a channel clear does not establish that condition. When sharing a band as a secondary station, also check whether another affected user is a primary station, a later licensed secondary service or a service covered by an exemption. Those cases use different paragraphs of section 12.
Apply secondary-service conditions
Under Spectrum Plan section 12, a secondary service must avoid causing harmful interference to primary services using the band, including those that start later. It cannot claim protection from harmful interference caused by those primary services. The section also protects activities or situations exempted under Division 4 of Part 1.4 of the Act and allows a claim of protection against harmful interference from another secondary service using the band if that other service was licensed later. Read the conditions of the particular licence alongside the allocation. For example, Class Licence section 15(1) prohibits causing harmful interference to radiocommunications generally.
Worked example. A personal station transmitting at 432.200 MHz receives a credible report that its transmissions seriously degrade a primary radiolocation service. Stop the operation producing the interference and establish the cause. Lowering power, choosing a suitable different frequency or correcting an unwanted emission can be appropriate after diagnosis. Confirm the change solves the problem before resuming the affected operation. If instead the amateur hears lawful primary radiolocation transmissions, section 12 precludes a claim for protection from that service on the basis of the secondary allocation. Use another suitable channel when needed.
Choose a power level and share the channel
A scheduled net or contest uses shared spectrum. Listen first. If the intended frequency is busy, arrange a different suitable frequency when practical. Choose a mode, bandwidth and power that achieve the contact while limiting unnecessary disturbance to other users.
For a clear local contact that works at 5 W, there is a practical reason to leave the amplifier off. The legal check is to meet the frequency, emission and power limits in the applicable licence and avoid harmful interference. Schedule 2 states maximums in terms that depend on the band, the emission and the power quantity. Directional antennas can improve the wanted path and reduce energy in some other directions. Their gain may increase exposure or EIRP in the main beam, so check any applicable EIRP cap and exposure condition.
Australian Radiofrequency Spectrum Plan · ACMA operating procedures · Amateur Class Licence · WIA Australian band plan
What are two consequences of operating an amateur station as a secondary service in an Australian band?
An amateur may interfere with primary operation whenever it is part of a scheduled net.
The secondary service must avoid causing harmful interference to primary services and cannot claim protection from harmful interference caused by them.
The two services alternate legal priority by day of the week.
The secondary service gains priority as soon as it makes a regular contact on the frequency.
A class-licensed transmission at 432.200 MHz is seriously degrading a primary radiolocation service. What is the appropriate response?
Increase power to establish a stronger amateur claim to the frequency.
Change mode and continue while the harmful interference persists.
Maintain the contact until the primary station moves.
Stop the operation causing harmful interference and correct the problem before resuming it.
A clear local contact works reliably at 5 W. Which statement correctly connects operating practice and Class Licence limits?
The operator must always use the full power listed for the qualification.
Holding an Advanced qualification removes the interference condition.
Power limits can be ignored when using a directional antenna.
Using 5 W is good practice here. The legal checks include the applicable Schedule 2 limit and section 15.
Sections you finish are checked off in the contents.