The instrument rests on a set of interlocking technical and procedural concepts. Define these first and then show how they operate in the text.

1. Frequency definitions and sub-bands (s 5)

   • 850 MHz band is defined as 814-845 MHz and 859-890 MHz (s 5(1)). The latter portion is called the 850 MHz Upper Sub-band (859-890 MHz). The split reflects the operational reality of the band being non-contiguous around 850 MHz.
   • 900 MHz band is defined as 890-915 MHz and 935-960 MHz (s 5(1)). The 900 MHz Lower Sub-band is 890-915 MHz (s 5(1)).

2. Wanted and unwanted signals (s 5(1))

   • The instrument distinguishes "wanted signal" (intended emission to the protected receiver) and "unwanted signal" (any radio emission not communicating with the protected receiver) (s 5(1)). These are the reference categories used in specifying protection metrics such as wanted-to-unwanted ratios and blocking levels (see ss 10-11).

3. First-in-time protection principle (ss 9(2), 12(2))

   • For several classes of apparatus-licensed receivers (trunked land-mobile and fixed links) the instrument treats protection as being on a first-in-time basis. Where an apparatus licence existed and the receiving station was licensed prior to a spectrum licensed transmitter being registered in the Register, that apparatus-licensed receiver is intended to receive protection in accordance with the instrument (ss 9(2), 12(2)).

4. Delegation to and reliance on RALI documents for technical criteria (s 8(3); s 10-11; s 13; s 15)

   • The instrument does not itself reproduce detailed protection ratios and blocking figures. Instead, it directs readers to the Radiocommunications Assignment and Licensing Instructions (RALIs): RALI LM 8 for trunked land-mobile protection ratios and blocking (ss 10-11); RALI FX 22 for fixed point-to-point link protection (s 13(1)); and RALI FX 16 for fixed point-to-multipoint service receivers (s 13(2)). The RALIs are incorporated by reference and are to be consulted as the source of numeric criteria.

5. Interference phenomena identified (s 7)

   • The instrument explains the mechanisms by which spectrum licensed transmitters can affect receivers: spurious emissions, blocking, and intermodulation (s 7(1)-(2)). These are the interference vectors that the protective criteria are intended to mitigate.

6. Cross-instrument definitions and determinations (s 5(2)-(3))

   • Terms used in the instrument have meanings drawn from other instruments. In particular, it states that terms defined in the Radiocommunications (Unacceptable Levels of Interference , 850/900 MHz Band) Determination 2021 have the same meaning as in that determination (s 5(2)). Similarly, terms from the Radiocommunications (Interpretation) Determination 2015 are adopted where used (s 5(3)).

7. Allocation and coordination pragmatics (s 8(4), s 14(2) note)

   • The instrument recommends modelling methods, specifically the ITU‑R Recommendation P.1144, when modelling propagation (s 8(4)), and records ACMA policy to downshift the 850 MHz band upper edge by 1 MHz before 17 June 2028 to 889 MHz (s 14(2) note). The downshift is treated as an expected partial easing of coexistence issues, but the instrument is drafted on the assumption the downshift has not occurred (s 14(2) note).

8. ACMA's role and evidentiary use (s 8(5))

   • ACMA will take the instrument into account when determining whether interference has occurred from a spectrum licensed transmitter to another licensed device, in the absence of separate agreements between affected licensees (s 8(5)). The instrument therefore functions as ACMA's baseline guidance for assessment.

9. Preservation of private negotiation (s 8(6))

   • The instrument explicitly does not prevent licensees negotiating different protection arrangements between themselves (s 8(6)). That preserves private contractual allocation of interference risk and potential bespoke technical solutions.

10. Specific numeric protection for aeronautical services (s 17)

    • For aeronautical systems appearing in the Register in 960-980 MHz under licence type "aeronautical system", the instrument prescribes a protection level: minus 129 dBW per MHz at the antenna connector, assuming a 9 dBi antenna gain if the Register does not specify gain and azimuth (s 17). This is a concrete numeric requirement within the instrument itself.

Together, these concepts establish a framework that: (a) specifies which receivers will be protected, (b) points to technical standards and RALI instructions for numerical application, (c) sets out priority rules via first-in-time protection, and (d) instructs ACMA to use this instrument as a reference point when assessing interference in the absence of negotiated arrangements (s 8(2)-(6); ss 9-13; s 15; s 17).

The instrument has direct operational effect on a defined set of participants in the Australian radiocommunications ecosystem. Who pays, who decides and what behaviour changes derive from the instrument’s text.

Primary affected parties

• Spectrum licensees operating in the 850/900 MHz band: The instrument places explicit obligations on spectrum licensees to ensure their authorised transmitters protect specified receivers to levels set out in RALI documents and in the instrument (for aeronautical systems) (see s 13, s 15, s 17). Spectrum licensees will therefore bear the direct compliance costs of any technical mitigation (filtering, power limits, site and antenna choices, coordination activities) necessary to meet the referenced protection criteria.
• Apparatus licensees with receivers in the protected bands: These include trunked land-mobile base and mobile receivers operating in bands listed at s 8(2)(a) and ss 10-11; fixed point-to-point and point-to-multipoint link receivers operating in the 804-806 MHz and 845-851 MHz bands (s 12(1)); and aeronautical navigation services registered in the 960-980 MHz band under the "aeronautical system" licence type (s 16(1), s 17). Apparatus licensees who had receivers licensed and registered before a spectrum licence or transmitter registration will receive protection on a first-in-time basis (s 9(2), s 12(2)). Those apparatus licensees therefore hold a protected entitlement that may constrain new spectrum licensee deployment options.

Secondary affected parties

• SOB link operators: Sound Outside Broadcast links usually operate in 845-846.5 MHz and are treated as temporary and transportable (s 12(1)-(2) background). SOB links in 845-851 MHz operate on a "no interference/no protection" basis in relation to primary fixed links and spectrum licensed services and are subject to a special licence condition that they must not cause interference to primary services. That places the operational burden on SOB operators to avoid interfering and means they receive no protection in return (s 12(2) note).
• Manufacturers and equipment vendors: Although not directly regulated in the instrument, equipment design choices (selectivity, filters, blocker handling) are implicated since the protection criteria assume certain receiver selectivity and bandwidth characteristics as specified or assumed in RALI LM 8 and RALI FX documents (see ss 10(2), 11(2), s 13). Vendors supplying receivers to apparatus licensees will find demand for devices that meet the assumed characteristics.
• ACMA (regulator): ACMA is instructed to take the instrument into account when determining whether interference has occurred and will administer the Register outcomes and first-in-time determinations (s 8(5); s 9(2); s 12(2)). ACMA also publishes and maintains the external RALI instruments referenced by this guideline (s 5(1) notes).

Tertiary effects

• Mobile network operators that hold spectrum licences: They must coordinate with adjacent-band licence holders and, where required, participate in mitigation measures and good-faith coordination referred to in s 14(2) (background) and s 15. This can affect network rollout planning, base station siting, and may impose additional capex/opex for filters or other mitigation solutions.
• Users of services reliant on protected receivers: For example, emergency services using land-mobile trunked systems, fixed-link backbone services for enterprise customers, and aeronautical navigation services. The instrument’s protection of these receivers is intended to maintain quality and reliability for these end users where apparatus licences pre-exist spectrum registrations (s 9(2); s 12(2); s 17).

Decision-making and incentives

• Who decides: the Register date establishes priority. ACMA applies the instrument in interference determinations when no private agreement exists (s 8(5); s 9(2); s 12(2)).
• Who pays: spectrum licensees are the primary payers for measures required to meet the protection obligations because the instrument requires spectrum licensees to ensure authorised transmitters protect receivers (s 13(1)-(2); s 15). Apparatus licensees will generally not bear those mitigation costs where their receivers have first-in-time priority, although they may incur costs to upgrade or document receiver performance to prove compliance.
• Behaviour changes: expect spectrum licensees to prioritise engineering mitigation, site selection, and coordination activities before or during deployment; apparatus licensees may need to ensure their registration details and technical data in the Register accurately reflect receiver characteristics to assert protection rights; SOB link operators will continue ad hoc operations but on a no-protection basis.

Geographic and temporal scope

• The instrument applies to receivers in or adjacent to the 850/900 MHz band but excludes parts of the spectrum or areas specified in the Radiocommunications (Spectrum Re-allocation - 850/900 MHz Band) Declaration 2020, as noted in s 8(1). It also anticipates a policy-driven band downshift by 1 MHz before 17 June 2028 (s 14(2) note) and therefore frames its guidance both for current and transitional arrangements.

In short, the instrument centralises protection obligations on spectrum licensees while preserving apparatus-licensed receivers' entitlements where they predate spectrum licence registration. It therefore reallocates practical compliance costs and operational constraints primarily to spectrum licensees, with consequences for network planning and equipment choices across the affected ecosystem.

The instrument assigns a mix of duties and entitlements. Below are the explicit duties spelled out in the text together with the rights and practical entitlements that follow.

Duties imposed on spectrum licensees

• Ensure protection of fixed point-to-point link receivers to levels detailed in section 4.2.2 and 6.2.2 of RALI FX 22 (s 13(1)). The instrument does not reproduce numerical values but makes these RALI sections the binding source for fixed link protection.
• Ensure protection of fixed point-to-multipoint service receivers according to the protection ratio and usable sensitivity level detailed in RALI FX 16 (s 13(2)).
• Ensure that authorised radiocommunications transmitters protect trunked land-mobile base station receivers and mobile receivers to the wanted-to-unwanted ratios and blocking levels specified in RALI LM 8, for the specified percentages of time and locations (ss 10(1)(c)-(d); 11(1)(c)-(d)). In addition, the instrument allows certain receiver assumptions (e.g. cavity filter response and intermediate frequency bandwidth) to be used for planning purposes (ss 10(2); 11(2)).
• Ensure protection for 900 MHz base station receivers as specified in section 16 of the Radiocommunications Advisory Guidelines (Managing Interference to Spectrum Licensed Receivers - 850/900 MHz Band) 2021 (s 15). The instrument requires cooperation and good faith participation in mitigation measures set out in that advisory guideline (s 14(2) background).
• Ensure that a spectrum licensed base station operating in the 900 MHz band protects registered aeronautical stations in 960-980 MHz to a level of minus 129 dBW/MHz at the antenna connector, with an assumed 9 dBi antenna gain where gain and azimuth are not specified in the Register (s 17).

Rights and entitlements of apparatus licensees

• First-in-time protection: An existing apparatus licensed receiver licensed prior to registration of a spectrum licensed transmitter in the Register is intended to receive protection in accordance with this instrument (s 9(2); s 12(2)). This gives apparatus licensees a presumption of protection if their licence registration precedes the spectrum registration.
• Ability to negotiate different protection arrangements: The instrument expressly preserves the parties’ ability to make different protection arrangements by agreement (s 8(6)). That is a contractual right to allocate interference risk differently from the instrument’s defaults.

Regulator duties and discretion

• ACMA will take the instrument into account in determining whether interference has occurred from a spectrum licensed transmitter (s 8(5)). That creates an evidentiary starting point or benchmark for ACMA decisions where there is no private agreement.
• The instrument also incorporates other instruments and external documents by reference (s 6). ACMA’s duty therefore includes publishing and maintaining or pointing to the RALI and other documents that provide the specific protection metrics.

Operational and technical rights and assumptions

• Receiver performance assumptions: For planning and coordination, the instrument allows base station radiofrequency selectivity to be assumed equivalent to a cavity filter response specified in RALI LM 8 and allows receiver intermediate frequency bandwidth and antenna characteristics to be assumed as specified in that RALI (s 10(2)). Equivalent assumptions exist for mobile receivers (s 11(2)). These assumptions permit spectrum licensees and planners to apply standardised receiver models when calculating interference risk rather than requiring bespoke measurement at each receiver site.

Special operational regimes

• SOB links: Sound Outside Broadcast links are subject to a "no interference/no protection" regime in the 845-851 MHz band, and SOB apparatus licences are subject to a special licence condition requiring no interference may be caused to any primary radiocommunications station or service (s 12(2) note). This effectively imposes an absolute duty on SOB operators to avoid causing interference and denies them recourse to protection against other services in that segment.

Limitations and preserved freedoms

• The instrument applies outside parts of the spectrum and named areas specified in the Spectrum Re-allocation Declaration 2020 (s 8(1)). It thus limits its own geographic/spectral reach and defers to that earlier declaration where applicable.
• The instrument does not itself create additional licence types or alter Register mechanics; it prescribes protection criteria that ACMA will consider; enforcement and licence conditions remain matters for ACMA under the Radiocommunications Act and related instruments.

Practical consequences of duties and rights

• Spectrum licensees must incorporate the RALI-specified protection criteria and the aeronautical protection level when engineering and deploying transmitters. The instrument therefore translates into technical duties affecting site selection, power levels and transmitter emissions specifications (ss 10-11, s 13, s 17).
• Apparatus licensees who wish to rely on first-in-time protection should ensure their apparatus licences and station details are accurately recorded in the Register prior to spectrum registration of adjacent-band transmitters (ss 9(2), 12(2)). The Register date is the primary factual determinant of priority under the instrument.

The instrument therefore sets duties on spectrum licensees to meet RALI-based protection metrics, preserves apparatus licensee protection where they predate spectrum registrations, and gives ACMA a benchmark to assess interference in the absence of private agreements (s 8(5)-(6); ss 10-13; s 17).

The instrument itself is an advisory guideline made under s 262 of the Radiocommunications Act 1992 (s 3). It does not create standalone criminal offences or prescribe monetary penalties in the text. The enforcement and penalties that may follow from conduct inconsistent with the instrument therefore arise indirectly through the Act, the Register and licence conditions referred to in other instruments.

What the instrument says about enforcement and ACMA’s role

• ACMA will take the instrument into account when determining whether interference has occurred from a radiocommunications transmitter operating under a spectrum licence in the 850/900 MHz band to another device operating under a different licence, in the absence of separate criteria agreed between affected licensees (s 8(5)). That means the instrument forms part of ACMA’s evaluative framework and will be used as a benchmark for whether interference is considered unacceptable or not, but the instrument does not itself specify enforcement actions.
• The instrument leaves open private negotiation between licensees (s 8(6)). Where parties have a private agreement that allocates protection differently, ACMA will take that into account. Enforcement of a privately negotiated arrangement would be a matter of contract between the parties and not something the instrument imposes.

Where statutory enforcement originates

• Enforcement, remedial action and penalties would be exercised under the Radiocommunications Act 1992 and the licence conditions created under that Act. The instrument was made under s 262 of that Act (s 3), so any enforcement action for breaching licence conditions or for causing unlawful interference will be grounded in the Act and related determinations and not in this advisory instrument itself.
• The instrument’s role is therefore to inform ACMA’s interference determinations and to be a reference in assessing whether a spectrum licensed transmitter has caused interference inconsistent with the Act or separate licence conditions. The instrument will be used as technical guidance and naming it in an ACMA determination could influence the remedy ACMA orders or the treatment of parties in any administrative enforcement process.

Practical enforcement pathways likely to be used (as implied by the instrument)

• Administrative remedies by ACMA: because ACMA will take the instrument into account (s 8(5)), ACMA could require changes to transmitter parameters, order cessation or reconfiguration of equipment, or impose licence conditions if it deems interference unacceptable under the Act, using the instrument as the technical anchor. The instrument itself does not enumerate these remedies, but ACMA’s authority under the Act would permit them.
• Contractual enforcement: Parties that choose to negotiate alternative protection arrangements may enforce those arrangements as contracts between licensees (s 8(6)). Failure to comply with such contracts would be a private law dispute, separate from ACMA action, unless ACMA enforces a related licence condition.
• No-protection special conditions: SOB links operate on a no interference/no protection basis and SOB apparatus licences carry a special licence condition prohibiting interference to primary services (s 12(2) note). Non-compliance with a licence condition could provide ACMA a direct statutory enforcement route under the Act.

Limitations and legal uncertainty

• The instrument’s being advisory and reliant on cross-referenced RALI and other instruments means that the precise technical threshold for ACMA to find interference will usually be drawn from those RALI documents or from the Act’s definitions and enforcement powers, not from this instrument alone (s 8(3); ss 10-11; s 13; s 17). Parties should therefore not rely on the instrument alone as determinative of enforcement outcomes.
• The instrument assumes certain receiver models and default antenna gains for calculation (for example, the 9 dBi antenna gain assumption in s 17 for aeronautical protection). Where the Register specifies other values, those will supplant the default. This introduces a factual element ACMA must evaluate in any enforcement decision.

In summary, the instrument is an ACMA advisory guideline that ACMA will use as a technical benchmark when assessing interference cases. Enforcement and penalties are exercised under the Radiocommunications Act and licence conditions, and the instrument guides, but does not itself prescribe, ACMA’s enforcement approach (s 3; s 8(5); ss 10-13; s 17).

This instrument is not standalone law; it sits within a network of primary legislation and other legislative instruments. The text explicitly cross-references and integrates several other instruments and Acts. Below are the key interactions and their operational implications.

Primary statutory authority

• The instrument is made under s 262 of the Radiocommunications Act 1992 (s 3). That Act provides the regulatory framework under which spectrum and apparatus licences are issued, the Register is maintained, and enforcement powers are exercised. Any enforcement action or alteration to licences that follows from disputes over interference will be grounded in the Radiocommunications Act, with this instrument functioning as advisory guidance.

Interaction with other legislative instruments and determinations

• Radiocommunications (Unacceptable Levels of Interference , 850/900 MHz Band) Determination 2021: Terms used in this instrument that are defined in that Determination have the same meaning in this instrument (s 5(2)). The instrument therefore imports definitions and thresholds from that Determination where they overlap.
• Radiocommunications (Interpretation) Determination 2015: The instrument adopts definitions from that Determination (or any instrument replacing it) for terms such as land mobile service, radionavigation and spurious emission, via s 5(3) and its note.
• RALI FX 16, RALI FX 22, RALI LM 8: The instrument directs readers to these RALI assignment and licensing instructions for detailed protection criteria, coordination arrangements and frequency assignment requirements (s 5(1) definitions; s 8(3); ss 10-11; s 13). These RALIs are legislative instruments or administrative instructions that ACMA publishes and updates periodically. The instrument adopts those documents by reference as the source of numerical and procedural detail.
• Radiocommunications Advisory Guidelines (Managing Interference to Spectrum Licensed Receivers - 850/900 MHz Band) 2021: The instrument requires cooperation and mitigation participation set out in Part 3, section 16, of that other guideline as part of protecting 900 MHz base station receivers from 850 MHz transmitters (s 14(2) background; s 15).

Interpretation and publication cross-references

• Section 6 of the instrument states that references to other legislative instruments are to those instruments as in force from time to time (s 6). It points to s 10 of the Acts Interpretation Act 1901 and subsection 13(1) of the Legislation Act 2003 for interpretation rules (s 6 Note 1). This is a standard drafting mechanism that means updates to RALI or interpretation determinations will flow through without amending this instrument.

Register and priority interactions

• The instrument relies on the Register as the factual basis of first-in-time protection. The Register is established under s 143 of the Act; the instrument explicitly references the Register in describing which apparatus-licensed receivers will receive protection if licensed prior to registration of a spectrum licensed transmitter (s 9(2) and s 12(2)). This embeds use of the Register in legal priority and coordination outcomes.

Spectrum re-allocation Declaration 2020

• The instrument applies outside the parts of the spectrum or named area specified in the Radiocommunications (Spectrum Re-allocation - 850/900 MHz Band) Declaration 2020 (s 8(1)). That Declaration therefore carves out parts of the spectrum or geographic areas where this instrument does not apply. Users must consult both instruments to determine applicability.

International standards

• The instrument recommends the use of ITU‑R Recommendation P.1144 for propagation modelling when planning in the 850/900 MHz band (s 8(4)). Although ITU recommendations are not domestic law, they are normative technical references that ACMA expects be considered when modelling and coordinating. Reliance on P.1144 is therefore an implicit tie to international technical methodology in domestic interference assessments.

Practical implications of these interactions

• Users must consult multiple instruments: the Radiocommunications Act for legal authority and enforcement mechanisms; the Register for priority dates and station parameters; the Unacceptable Levels Determination and RALI documents for numerical protection criteria; the other advisory guideline for mitigation measures between 850 and 900 MHz licensees; and ITU guidance for propagation modelling (ss 3; 5; 6; 8(3)-(5); 14(2) note; s 17).
• Because references are to instruments "as in force from time to time" (s 6), updates to RALI instructions or determinations will change the practical content of protection criteria without amendment to this instrument. That creates ongoing compliance obligations to monitor those instruments.
• Where private agreements exist, those contractual arrangements may alter the practical application of the instrument because s 8(6) preserves negotiation rights, but ACMA’s evaluative baseline remains the instrument unless an agreement sets different criteria.

In short, this instrument is a node within a regulatory web. It sets priorities and points to technical detail in other instruments; it does not replace the Radiocommunications Act, the Register, the RALIs, the Unacceptable Levels Determination, or ACMA’s other advisory guidelines. Compliance therefore requires consulting all of those sources together (s 3; s 5; s 6; s 8(3)-(6)).

The instrument’s text provides a limited, but specific, amendment history embedded in its own provisions. The relevant items in the instrument and their dates are as follows.

Revocation of earlier guidelines

• The instrument expressly revokes the Radiocommunications Advisory Guidelines (Managing Interference from Spectrum Licensed Transmitters - 800 MHz band) 2012 (F2012L01775) (s 4). The revocation is unilateral and is effected upon the instrument’s commencement. No transitional provisions are set out in the instrument itself concerning actions that were taken or obligations that arose under the revoked 2012 guidelines; the instrument simply revokes the earlier instrument.

Commencement

• The instrument comes into force at the start of the day after the day it is registered on the Federal Register of Legislation (s 2). The instrument therefore becomes effective immediately upon registration with the Federal Register, from the first full day thereafter. The instrument’s notes emphasise the availability of the Federal Register for checking registration and instrument status.

No recorded amendments in the text

• The text supplied contains no express amendment lines other than the revocation noted in s 4 and the standard commencement provision in s 2. There are no schedules of amendments, no historical marginal notes indicating prior versions, and no savings clauses beyond the first-in-time protection commitments (for example s 9(2), s 12(2)).

Cross-referenced instruments may change

• Section 6 makes references to other instruments subject to amendment "as in force from time to time" (s 6). That drafting choice means that, although this instrument may remain unchanged, its practical content will evolve as RALI FX 16, RALI FX 22, RALI LM 8, the Radiocommunications (Unacceptable Levels of Interference , 850/900 MHz Band) Determination 2021, the Radiocommunications (Interpretation) Determination 2015, and the Radiocommunications Advisory Guidelines (Managing Interference to Spectrum Licensed Receivers - 850/900 MHz Band) 2021 are updated. Thus, while the instrument has a short in-text amendment history, it is designed to operate dynamically against living external instruments.

Implication for practitioners

• To track substantive change that affects obligations under this instrument, practitioners need to monitor:
  • updates to the Register and any changes to entries that affect antenna gain and azimuth assumptions (s 17);
  • updates to RALI LM 8, RALI FX 16 and RALI FX 22 for protection ratios and coordination arrangements (s 8(3); ss 10-11; s 13);
  • any amendments to the Radiocommunications (Unacceptable Levels of Interference , 850/900 MHz Band) Determination 2021 and the Radiocommunications (Interpretation) Determination 2015 for definitions and thresholds (s 5(2)-(3));
  • ACMA policy decisions relevant to the 803-960 MHz band, including the planned downshift of the 850 MHz upper boundary to 889 MHz by 17 June 2028, which the instrument references as an expected policy action but assumes has not yet occurred (s 14(2) note).

Because amendments to external instruments will alter the protection metrics this instrument references, the instrument’s amendment history is operationally dependent on the broader instrument ecosystem rather than on in-text changes to this guideline itself (s 6).

The instrument as supplied contains no references to judicial or tribunal decisions, and it names no cases. The text does not record any judicial review proceedings, administrative appeals, or other litigation arising from its content (there are no cited cases or litigation history sections). Therefore, based on the instrument text alone:

• There is no litigation history recorded within the instrument.
• The instrument does not cite precedent or state how courts or tribunals have treated similar guidelines in the past.
• Any enforcement or disputes arising under the instrument would be resolved through the Radiocommunications Act mechanisms and ACMA processes unless taken to court, but the instrument contains no account of such proceedings.

What practitioners should note about litigation risk

• Because the instrument is an advisory guideline and ACMA will take it into account when determining whether interference has occurred (s 8(5)), disputes between spectrum licensees and apparatus licensees could lead to administrative determinations by ACMA that may then be litigated or reviewed in court or tribunal proceedings. However, the instrument itself contains no record of past litigation nor statutory guidance on appeal routes.
• Practitioners advising clients should therefore treat the instrument as one of the technical and procedural materials ACMA will use in administrative decision-making, rather than as a codified source of judicially interpreted legal obligations. If conflicts arise, parties should expect the interplay of the Radiocommunications Act, Register evidentiary facts, RALI technical criteria and any private agreements to be central to litigation or review arguments.

In short, the instrument contains no litigation history in its text. Any litigated interpretation will come from subsequent disputes and case law that are not recorded here.

The instrument includes a number of practical traps and non-obvious features that can produce surprises for licence holders, engineers and planners. Below are the salient points to watch for, with references.

1. The instrument is advisory but ACMA will use it evaluatively (s 8(5))

   • Gotcha: Even though this is an advisory guideline rather than a prescriptive code setting out sanctions, ACMA will take it into account when determining interference. Practitioners should not treat "advisory" as the same as "no legal consequence". In the absence of a negotiated arrangement, ACMA will use this instrument as the benchmark (s 8(5)).

2. First-in-time protection depends on Register timing (ss 9(2), 12(2))

   • Gotcha: Protection is promised to apparatus-licensed receivers licensed prior to the registration of a spectrum licensed transmitter in the Register. That means protection rights depend on accurate, timely entries in the Register. Parties who expect protection should ensure registrations are up to date and that the Register contains the correct technical parameters.

3. Numeric protection values are mostly externalised to RALI and other instruments (s 8(3); ss 10-11; s 13; s 15)

   • Gotcha: The instrument does not contain most of the numerical protection criteria. To know what the wanted-to-unwanted ratios, blocking levels, protection ratios, and usable sensitivity levels are, users must consult RALI LM 8, RALI FX 16, RALI FX 22 and the other advisory guideline cited (s 8(3); ss 10-11; s 13; s 15). The RALI documents are referenced "as in force from time to time" (s 6), so the specific numbers can change without amending this instrument.

4. The SOB link "no interference/no protection" regime (s 12(2) note)

   • Gotcha: SOB operators in 845-851 MHz operate on a no-protection basis and have a licence condition prohibiting interference to primary services. They bear the entire risk and have no entitlement to protection. This is a hard operational constraint for temporary broadcast links.

5. The instrument assumes certain receiver parameters for modelling (ss 10(2), 11(2))

   • Gotcha: The instrument permits assumption of specific receiver selectivity, intermediate frequency bandwidth and antenna response for planning purposes. If an apparatus licensee’s actual receiver performance is worse than the assumed model, resolving disputes could become factual and technical and may disadvantage the party that relies on a different receiver characteristic. Practitioners should verify actual receiver specifications and ensure they match the RALI assumptions.

6. Cross-reference to other guidelines for mitigation (s 14(2) background)

   • Gotcha: Protection of 900 MHz base station receivers from 850 MHz transmitters requires cooperation and participation in mitigation measures set out in a separate ACMA advisory guideline (Part 3, s 16 of the Managing Interference to Spectrum Licensed Receivers guideline). Parties must consult and be prepared to act under that other guideline; failure to co-operate may result in first-in-time coordination outcomes.

7. The explicit aeronautical numeric protection rule uses a default antenna gain (s 17)

   • Gotcha: Section 17 specifies protection of aeronautical stations in 960-980 MHz to minus 129 dBW/MHz at the antenna connector, assuming 9 dBi antenna gain if the Register does not state gain and azimuth. If the Register contains different antenna parameters, those take precedence. Practitioners must check Register entries rather than rely on the default.

8. The instrument excludes parts of the spectrum named in the Spectrum Re-allocation Declaration 2020 (s 8(1))

   • Gotcha: The instrument’s coverage is not uniform across the band and spatially. Licence holders must check the Spectrum Re-allocation Declaration 2020 to determine whether the instrument applies in a given part of the spectrum or in a named geographical area.

9. Assumption of a future downshift that has not yet happened (s 14(2) note)

   • Gotcha: The instrument notes ACMA policy to downshift the 850 MHz band by 1 MHz before 17 June 2028 to 889 MHz and states the instrument assumes the downshift has not occurred. This creates a potential mid-term change in coexistence dynamics; parties should not assume the downshift has already eliminated coexistence issues and should plan for current boundaries unless and until the downshift is enacted and reflected in Register and licence conditions.

10. The instrument refers to international propagation modelling guidance (s 8(4))

    • Gotcha: The instrument recommends ITU‑R P.1144 for propagation modelling inputs and warns that different propagation models may be appropriate in particular contexts. This introduces modelling choice and sensitivity into interference assessments. Parties should document model choice and parameters, since ACMA expects consideration of P.1144 but modelling selection could affect outcomes.

11. Multiple cross-references and "as in force from time to time" wording (s 6)

    • Gotcha: The practical content of the instrument is dependent on other living documents. Licence holders must actively monitor RALI and determination updates because the instrument endorses the "as in force from time to time" approach. Failing to monitor those instruments could result in compliance gaps.

12. No express compensation or cost-shifting mechanism in the instrument

    • Gotcha: The instrument assigns protection obligations but does not create a statutory compensation regime for costs incurred in mitigation. Spectrum licensees are required to ensure protection, but the instrument does not specify how costs of mitigation are to be allocated between parties. Parties seeking compensation or cost-sharing arrangements must negotiate them privately (s 8(6)) or seek remedies under the Act if ACMA orders specific actions.

These are the practical "gotchas" that follow directly from the instrument’s drafting and cross-references. Each can generate disputes that require technical evidence and careful documentary records to resolve.

Compliance with the instrument requires attention to the Register, the RALI documents it references, the Register entries for station parameters, and active coordination. Below is a practical checklist grounded in the instrument text points and the likely steps an affected licensee or practitioner should take.

1. Identify whether the instrument applies to your operations

   • Check the frequency ranges defined in s 5 to confirm whether your transmitters or receivers sit in the 850 MHz band (814-845 MHz and 859-890 MHz), the 900 MHz band (890-915 MHz and 935-960 MHz) or the adjacent protected bands listed in s 8(2).
   • Confirm the geographic/spectrum exclusions in the Radiocommunications (Spectrum Re-allocation - 850/900 MHz Band) Declaration 2020 so you know whether this instrument applies in your area (s 8(1)).

2. Determine your legal status and entitlements

   • Are you a spectrum licensee or an apparatus licensee? The instrument assigns different duties and entitlements to each (ss 8(2); ss 10-11; s 13; s 15; s 17).
   • If you are an apparatus licensee, verify the date your receiver station(s) were registered in the Register and whether that registration pre-dates the registration of any adjacent spectrum licensed transmitter. First-in-time protection applies to apparatus licensed receivers licensed prior to a spectrum licence registration (s 9(2); s 12(2)).

3. Consult and apply the cross-referenced technical instruments

   • For trunked land-mobile protection criteria, consult RALI LM 8 for the wanted-to-unwanted ratios, blocking levels, assumed filter responses and intermediate frequency bandwidths used for planning and coordination (ss 10-11).
   • For fixed point-to-point links, consult RALI FX 22 (sections 4.2.2 and 6.2.2) for the numeric protection levels (s 13(1)).
   • For fixed point-to-multipoint services, consult RALI FX 16 for protection ratios and usable sensitivity levels (s 13(2)).
   • For 900 MHz base station protection specifics, consult section 16 of the Radiocommunications Advisory Guidelines (Managing Interference to Spectrum Licensed Receivers - 850/900 MHz Band) 2021 (s 15).
   • Ensure you use the versions of those instruments that are in force at the time of planning because s 6 references instruments as in force from time to time.

4. Check Register entries and station parameters

   • For aeronautical systems that you must protect or that must protect others, check the Register for station entries in 960-980 MHz under licence type "aeronautical system" and confirm antenna gain and azimuth values. If those are absent, s 17 tells you ACMA will assume 9 dBi gain. Use the actual Register values where present (s 17).
   • Ensure all your own apparatus licence details are correctly and fully recorded in the Register to secure first-in-time protection where applicable (s 9(2); s 12(2)).

5. Undertake propagation modelling and engineering studies

   • Use ITU‑R Recommendation P.1144 as a primary guide when selecting propagation models and when modelling path loss in the 850/900 MHz band, unless another method is suitable and justified (s 8(4)). Document your choice of propagation model and inputs because ACMA expects the P.1144 recommendation to be considered.
   • Apply the receiver assumptions specified in relevant RALI documents where the instrument allows them (for example cavity filter response and IF bandwidth in RALI LM 8) to compute interference margins and wanted-to-unwanted ratios (ss 10(2), 11(2)).

6. Plan for and implement technical mitigation

   • For spectrum licensees: design transmitter deployments, power levels, antenna patterns, and any filtering or emissions-shaping measures to meet the RALI-specified protection ratios, blocking limits and fixed-link protection requirements (ss 10-11; s 13; s 15).
   • For apparatus licensees: ensure receiver installations (antenna height, location, filtering) meet the expected parameters and maintain technical documentation and test results that demonstrate conformance to the assumed receiver models used in coordination.

7. Coordinate proactively and in good faith

   • Where required by the instrument and cross-referenced guidelines, engage in good-faith coordination and mitigation discussions with adjacent licence holders, particularly where 900 MHz base station receivers and 850 MHz transmitters operate across the 890 MHz boundary (s 14(2) background; s 15).
   • Document coordination attempts, offers and responses, because ACMA will consider whether parties negotiated separate arrangements or relied on the instrument when determining interference (s 8(5)-(6)).

8. For SOB operators, respect the no-protection rule

   • If operating SOB links in 845-851 MHz, note that you operate on a no interference/no protection basis with a licence condition requiring no interference to any primary service (s 12(2) note). Do not plan operations on the assumption you will receive protection.

9. Maintain records and measurement evidence

   • Keep measurement logs, site plans, propagation model inputs and outputs, Register screenshots showing station registration dates and parameters, and copies of RALI documents applicable at the time of planning. These will be critical if ACMA is asked to determine whether interference has occurred (s 8(5)).

10. Monitor relevant instruments and policy decisions

    • Because the instrument imports RALI and other documents "as in force from time to time" (s 6), subscribe to ACMA updates for RALI LM 8, RALI FX 16, RALI FX 22 and the Unacceptable Levels Determination. Also track ACMA policy decisions relevant to the 803-960 MHz band, such as the planned 1 MHz downshift to 889 MHz before 17 June 2028 (s 14(2) note).

11. If disputes arise, consider contractual options and administrative remedies

    • Parties may negotiate private protection arrangements that depart from the instrument defaults (s 8(6)). If negotiation fails and interference occurs, ACMA will use the instrument as the benchmark in the absence of a separate agreement (s 8(5)). Seek both contractual remedies and administrative review options under the Radiocommunications Act where appropriate.

12. Engage specialised technical and legal advice

    • The instrument’s practical application requires technical modelling, familiarity with RALI requirements, and an understanding of ACMA processes and the Register. For complex deployments, obtain expert RF engineering input and legal advice before deploying or modifying transmitters adjacent to protected receivers.

Following this compliance roadmap will position a licensee or a practitioner to demonstrate good faith in coordination, meet the RALI-derived protection metrics, and document the steps ACMA will expect in any interference assessment (ss 8-13; s 17).