Login Start free Dashboard Logout

Frequency Coordination

Frequency Coordination Tool

Find clean, interference free TX and RX frequency pairs with full intermodulation analysis for surface and underground radio systems.

Start your free trial → Sign in

Included in the 14-day Pro trial on every new account. No credit card.

System type in the top bar, with the panel open on the Existing tab.
System type in the top bar, with the panel open on the Existing tab.
ACMA site lookup. Imported carriers carry an ACMA provenance chip.
ACMA site lookup. Imported carriers carry an ACMA provenance chip.
Completed request: ranked pairs, separation metrics, and the spectrum view.
Completed request: ranked pairs, separation metrics, and the spectrum view.

Overview

Frequency coordination is the engineering process of selecting transmit and receive frequency pairs that will not generate harmful intermodulation products in the band of interest. Done badly, it produces in band spurs that mask weak signals, drive trunked systems into hunting, and trigger persistent intermittent interference that is notoriously difficult to diagnose once the network is in service.

The noIM₃ Frequency Coordination Tool runs an exhaustive search across user defined TX and RX frequency ranges, applies split, guard band, and exclusion zone constraints, then scores every candidate pair against ITU standard intermodulation models, to 5th order on the surface and to 3rd order underground, where 5th order is omitted. Results are ranked so the cleanest, lowest risk pairs surface first, making the tool suitable for both greenfield deployments and incremental channel expansion within a working network.

Surface mode evaluates the full product set: 2nd order, 3rd order two signal and three signal, and 5th order two signal and three signal, plus harmonics of the transmit carriers. Underground mode evaluates 2nd and 3rd order and omits 5th order, because the 5th order three signal family is effectively un-plannable and the two signal product sits below the noise floor once typical leaky feeder coupling loss and cascade amplifier IM rejection are taken into account. Underground mode also drops the TX/RX role filter, so every carrier both radiates harmonics and counts as a potential victim, which is how leaky feeder systems in mines, tunnels, and metro networks behave. Underground adds one further choice: whether to combine a downlink carrier with an uplink one. A diplexed line amplifier filters each direction into its own gain stage, so the two never meet at the same active non-linearity and a mixed band product can only form as passive intermodulation on the cable. Restricting the enumeration to each band on its own removes those products; including them is available for a site where cable PIM is the concern.

Capabilities

Automated frequency pair generation

Scans every valid TX and RX combination inside the configured ranges and split, then filters for guard band compliance and existing channel collisions before scoring.

ITU standard intermodulation engine

2nd, 3rd, and 5th order product analysis on every candidate. Surface mode reports the full set, two signal and three signal. Underground mode reports 2nd and 3rd order and omits 5th order for leaky feeder environments.

Ranked pair scoring

Each pair receives a composite score combining intermodulation hit count, minimum separation, and spectral cleanliness, so the cleanest options surface at the top of the list.

Guard bands and exclusion zones

Enforces engineering and licensing constraints. Guard bands, exclusion ranges, and protection of incumbent channels are applied at search time, not as an afterthought filter.

Interactive spectrum visualisation

Carriers and intermodulation products overlaid on the band, so you can validate coordination outcomes visually before committing to a channel plan.

Manual frequency entry

Pin specific TX or RX frequencies (for example fixed dispatch channels) and let the tool coordinate the remainder of the plan around them.

Standards & methodology

  • ITU SM.1446. Intermodulation interference reference
  • ITU SM.337. Frequency separation between adjacent transmissions
  • ITU SM.329. Unwanted emissions in the spurious domain
  • ACMA spectrum management framework alignment for Australian deployments

When to use this tool

  • Selecting clean frequency pairs for new radio system deployment
  • Expanding an existing trunked or conventional network without introducing self interference
  • Designing underground communication systems in mining and tunnelling environments
  • Predeployment engineering validation for mission critical and life safety networks
  • Generating coordinated channel sets for contractors and field technicians
  • Producing spectrum interaction visualisations for engineering reports and licence applications
  • Coordinating frequency plans for emergency services and resource sector radio fleets
  • Validating vendor proposed channel plans before purchase or rollout
  • Diagnosing in band interference issues on operational networks
  • Planning channel reuse strategies across multi site deployments
  • Supporting ACMA licence applications with documented coordination output
  • Coordinating fleetwide channel changes during band restructures or refarming activity

Frequently asked questions

What is frequency coordination and why does it matter?

Frequency coordination is the process of choosing TX and RX frequency pairs that do not generate harmful intermodulation products inside the band of interest. Without it, a system will produce in band spurs that mask weak signals and cause intermittent interference that is very difficult to diagnose once the network is in service.

Which intermodulation orders does the tool evaluate?

Surface mode evaluates 2nd order, 3rd order two signal and three signal, and 5th order two signal and three signal, plus harmonics of the transmit carriers. Underground mode evaluates 2nd and 3rd order and omits 5th order. The product types follow the definitions in ITU-R SM.1446. Note that SM.1446 defines and measures intermodulation products rather than predicting their level: this tool computes frequency arithmetic and channel spacing, and models no isolation, filtering, or predicted product level.

How is each frequency pair scored?

Each candidate pair is scored on a composite of intermodulation hit count weighted by order, minimum separation between carriers and intermodulation products, and spectral cleanliness across the working band. Higher scores indicate cleaner, lower risk pairs and surface first in the ranked output.

Can I protect existing channels and exclusion zones?

Yes. The constraint engine enforces user defined existing channels, guard bands, and exclusion ranges (for example licensed incumbents or broadcast bands) at search time. Pairs that would violate any constraint are eliminated before scoring rather than filtered after the fact.

Does it support manual frequency entry?

Yes. You can pin specific TX or RX frequencies, for example fixed dispatch or repeater channels that cannot move, and the tool will coordinate the remaining channels around them.

Is the tool suitable for underground or mine radio coordination?

Yes. Underground mode evaluates 2nd and 3rd order products and omits 5th order: the 5th order three signal family is effectively un-plannable, and the two signal product sits below the noise floor once typical leaky feeder coupling loss and cascade amplifier IM rejection are taken into account. It also drops the TX/RX role filter that surface mode applies, because leaky feeder coupling makes the distinction between a radiating carrier and a listening one moot in tunnels and stopes. Separately, underground lets you choose whether downlink and uplink carriers are combined with each other: a diplexed line amplifier keeps the two directions in separate gain stages, so mixed band products can only arise as passive intermodulation on the cable rather than in the amplifier.

Does the tool align with ACMA spectrum management practice?

Yes. The coordination output is structured to support ACMA licence applications and Australian spectrum management workflows, with traceable input parameters, ranked candidate output, and exportable spectrum diagrams suitable for inclusion in engineering submissions.

Further reading