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Frequency Coordination

Frequency Plan Validator

Audit any existing radio frequency plan for intermodulation hits. Bandwidth aware proximity classification across 2nd, 3rd, and 5th order products with no plan changes required.

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Site metadata, system mode, and scoring mode set on the configuration panel.
Site metadata, system mode, and scoring mode set on the configuration panel.
Single carrier entry on the left, DL / UL repeater pair entry on the right.
Single carrier entry on the left, DL / UL repeater pair entry on the right.
Sortable hit table with formula, contributors, separation, zone, predicted dBm, and margin.
Sortable hit table with formula, contributors, separation, zone, predicted dBm, and margin.
Spectrum view with carriers, bandwidth shading, and Direct hits highlighted in red.
Spectrum view with carriers, bandwidth shading, and Direct hits highlighted in red.

Overview

Most radio sites in operation today were not designed dirty. They became dirty over time as channels were added, splits were adjusted, and incumbents moved into adjacent spectrum. The radios still key, the audio still passes, but range shortens, weak users drop out, and intermittent in band interference starts showing up in complaints. Before anyone reaches for new antennas, new repeaters, or a full redesign, the right first question is simpler. Is the existing frequency plan generating intermodulation interference, and if so, where?

The noIM₃ Frequency Plan Validator answers exactly that question. Submit your current channel list and the engine evaluates every frequency combination for 2nd, 3rd, and 5th order products in surface mode, or 2nd, 3rd, and 5th order with 3rd order focus in underground mode. Each product is then checked against every active carrier using a bandwidth aware proximity model, so a 100 kHz wideband channel has proportionally wider hit zones than a 12.5 kHz narrowband channel.

Output is a complete intermodulation audit. A zone breakdown table classifies each hit as direct, critical near, marginal, or watch. A sortable hit table shows the offending intermodulation frequency, the order, the full formula, the contributor channels, the target channel, and the separation in kHz. A frequency impact analysis shows which channels are the worst sources and the most affected victims. A pair interaction table identifies the most dangerous combinations. A spectrum view renders carriers as spikes and overlays direct hits in red. Computation runs entirely in your browser. No data leaves your machine.

Capabilities

Bandwidth aware hit zone classification

Each hit is classified by proximity to the target carrier, scaled against that carrier bandwidth. Direct hit means the intermodulation product falls within plus or minus half the channel bandwidth (co channel, in band interference). Zone 1 (critical near) extends from half BW to half BW plus 12.5 kHz. Zone 2 (marginal) covers half BW plus 12.5 to 25 kHz. Zone 3 (watch) covers half BW plus 25 to 50 kHz. Zones scale per carrier, so a 100 kHz channel has a much wider direct hit zone than a 12.5 kHz channel.

Surface and underground analysis

Surface mode evaluates 2nd, 3rd, and 5th order products typical of open air systems. Underground mode focuses on 3rd order dominance, which reflects the confined environment behaviour observed in mining, tunnelling, and metro radio installations where higher orders are heavily attenuated by structure loss.

Full hit table with formulae and contributors

Every intermodulation product that falls within any proximity zone is recorded as a row. Intermodulation frequency, order, full formula, contributor channel labels, target channel, separation in kHz, and zone classification. Sorted by severity, direct hits first, then by increasing separation. Exportable as CSV for inclusion in interference reports or client deliverables.

Frequency impact analysis

Two impact tables break the problem down by channel. The per frequency table shows each channel as both source (how many products it contributes to and how many direct or near hits it causes) and victim (how many direct and near hits land on it). Channels are colour coded by risk level. The pair interaction table identifies which frequency pairs generate the most hits when combined.

Spectrum view with direct hit highlighting

All carriers render as vertical spikes with bandwidth shading. Every in band intermodulation product is overlaid. Direct hits are drawn in red on top of the carrier spike, making problematic channels immediately obvious. Near miss products appear as blue markers between carriers. Colour coding matches the zone classification system used throughout the tool.

Most impacted channels and most problematic pairs

Headline summaries surface the worst victim channels and the most dangerous source pairs at the top of the result. Useful for prioritising which channels to investigate first when remediation effort is constrained, and for justifying which pairs to separate in a follow on optimisation pass.

CSV export and report ready output

The full hit table exports as CSV ready to drop into an interference report, a regulatory submission, or a client deliverable. The structure preserves all formulae, zones, and contributor labels, so the export is reviewable line by line by another engineer rather than being a black box.

Browser only computation

The validator runs entirely in your browser. No frequency data is transmitted to a server, which matters when the plan is operationally sensitive, commercially confidential, or covered by an information security regime that prohibits sending raw spectrum data to third party services.

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

  • Auditing a brownfield radio system before a planned maintenance shutdown
  • Reviewing a vendor or consultant proposed greenfield plan before acceptance
  • Identifying which channels are causing interference complaints in an operational system
  • Validating a new channel addition to an existing plan before programming radios
  • Producing an intermodulation audit report for a client or regulatory submission
  • Comparing surface and underground analysis assumptions for a mine site plan
  • Prioritising frequency coordination work by surfacing the worst source pairs
  • Confirming a plan is clean before deploying into a congested spectrum environment
  • Supporting ACMA licence renewal or variation with documented intermodulation evidence
  • Investigating intermittent in band interference reports without modifying the plan
  • Preparing the input for a follow on Frequency Plan Optimiser run
  • Teaching new RF engineers how intermodulation products land on real channel plans

Is this the right tool for you?

Reach for the Frequency Plan Validator in any of the following situations.

  • You have an operational radio network and you are getting intermittent interference complaints, and you want to confirm whether the existing plan is the source before reaching for replacement hardware.
  • You are about to add a new channel to an existing plan and want to confirm that the addition will not generate intermodulation hits on channels that are currently clean.
  • You have inherited a radio plan with no documentation and need a defensible audit of how clean it actually is before you take operational responsibility for the network.
  • You are reviewing a frequency plan submitted by a vendor or consultant and want an independent intermodulation audit before you accept the work.
  • You are preparing for a planned radio maintenance shutdown and want to know which channels need attention so the work scope is right sized rather than guessed.
  • You are responsible for a mine, tunnel, or industrial site and need underground appropriate intermodulation analysis rather than surface system assumptions.
  • You are producing an interference investigation report for a client or regulator and need a structured CSV hit table with formulae, contributors, and zones.
  • You are operating in congested spectrum (urban, port, mining province) and want to confirm a candidate plan is clean before deployment.
  • You are a consulting RF engineer pitching a frequency coordination engagement and need a fast audit that demonstrates the value of the work to a prospective client.
  • You are running an emergency services or safety critical radio plan and need to verify that the plan does not have direct hits on priority channels.
  • You are operating under a security regime that prohibits sending raw spectrum data to third party services and need an audit that runs entirely in the browser.
  • You are preparing the input for a Frequency Plan Optimiser run and want to first quantify the existing intermodulation problem to baseline the improvement.
  • You are training new RF engineers in frequency coordination and want a teaching tool that shows how intermodulation products land on actual channel plans rather than abstract examples.
  • You are validating that a recent channel addition or split change has not pushed previously clean channels into a hit zone.
  • You are responsible for ACMA licence renewal or variation and want documented intermodulation evidence to support the channel choices on the application.

Frequently asked questions

How is this different from the Frequency Plan Optimiser?

The validator audits an existing plan and reports where intermodulation hits land, without changing anything. The optimiser takes the same input and proposes precision channel shifts to clean it up. Use the validator first to baseline the problem and produce evidence. Use the optimiser to actually fix it. Both tools share the same intermodulation engine.

What does bandwidth aware proximity actually mean?

Hit zone thresholds scale with each individual channel bandwidth rather than a fixed value across the plan. A 100 kHz wideband channel has a direct hit zone of plus or minus 50 kHz. A 12.5 kHz narrowband channel has a direct hit zone of plus or minus 6.25 kHz. The result is that mixed bandwidth plans get a fair audit rather than every wideband channel being flagged or every narrowband channel being missed.

Which intermodulation orders are evaluated?

In surface mode, 2nd order (fg plus or minus fh), 3rd order two signal (2fg minus fh) and three signal (fg plus fh minus fm), and 5th order two signal and three signal products are evaluated. Underground mode focuses on 3rd order dominance, which is the order that actually matters in confined environments where higher orders are heavily attenuated by structure loss.

Does any frequency data leave my browser?

No. Computation runs entirely in your browser. No frequency data is submitted to a server. This matters when the plan is operationally sensitive, commercially confidential, or covered by an information security policy that prohibits sending raw spectrum data to third party services.

What does the CSV export contain?

One row per hit, with intermodulation frequency, order, full formula, contributor channel labels, target channel, separation in kHz, and zone classification. Sorted by severity. Suitable for inclusion in interference reports, client deliverables, or as the input record for a follow on optimisation pass.

Can I use this on a greenfield plan before deployment?

Yes. The validator does not care whether the plan is operational or proposed. Submit a candidate plan and you get the same intermodulation audit. Useful for confirming a vendor or consultant submitted plan is actually clean before you accept it, or for sanity checking your own greenfield design before programming radios.

How are direct, critical near, marginal, and watch zones defined?

Direct is within plus or minus half the channel bandwidth (co channel, in band interference). Zone 1 critical near extends from half BW to half BW plus 12.5 kHz. Zone 2 marginal covers half BW plus 12.5 to 25 kHz. Zone 3 watch covers half BW plus 25 to 50 kHz. Each zone has a distinct colour throughout the table, summary, and spectrum view.