Frequency coordination and intermodulation tools
Choose clean channels for a new service, check what they do on a shared site, and audit and clean up a plan that has grown dirty over the years.
Free tools stay free on a Standard account. Pro tools are included in the 14-day trial on every new account. No credit card.
How the design is done
Frequency coordination is choosing transmit and receive frequencies that work at the site without interfering with, or being interfered with by, the services already there. For land mobile radio that means intermodulation first. When several transmitters share a site, sums and differences of their carriers land at predictable frequencies, and a product on a working channel masks weak signals and causes interference that is hard to diagnose once the network is in service.
The arithmetic is exact, but the grading is a choice. Whether a product counts as a hit depends on how close it lands to the victim channel, and that threshold should follow the channel width: a wideband carrier has wider hit zones than a 12.5 kHz narrowband one. ITU-R SM.1134-1 and ACMA RALI LM 08 Annex D draw the boundary differently, so a result should always say which rule it was graded to.
Underground is different again. On leaky feeder in mines and tunnels every carrier can be a victim, and 5th order products are left out, because the three signal family cannot be planned around and the two signal product sits below the noise floor once coupling loss and amplifier intermodulation rejection are counted.
Most sites also grow dirty over time as channels are added. The tools below cover both jobs: choosing new channels, then auditing and cleaning up a plan that already exists.
The workflow, one tool per step
Find clean channel pairs
Search your TX and RX ranges exhaustively, apply the split, guard bands and exclusion zones, and rank every candidate pair by the intermodulation it creates: to 5th order on the surface and 3rd order underground.
Frequency Coordination Tool ProCheck them against the site
Import the licensed services on the site from the ACMA register, mark which carriers are your proposed change, and see what you would put into someone else’s receiver separately from what the site would put into yours.
Intermodulation Calculator ProAudit the plan you already have
Submit an existing channel list and grade every product (to 5th order on the surface) against ITU-R SM.1134-1, RALI LM 08 Annex D Table D2 or a custom separation, with the worst sources, the most affected victims and the most dangerous pairs listed.
Frequency Plan Validator ProClean it up with small shifts
Instead of a redesign, shift each channel within its tunable steps to leave the fewest products on the carriers, with priority weights that hold safety and dispatch channels to the smallest shifts. The output is a before and after comparison and a CSV reprogramming table for the technician.
Frequency Plan Optimiser Pro
Often used alongside
Further reading
- What Is Intermodulation (IM3)? Third-Order Products, IP3 and How to Avoid It Intermodulation is interference made when signals mix in a non-linear device. Why 2f1 minus f2 products land closest to the carriers, IP3, and how to avoid it.
- How to Get a Radio Licence in Australia: Apparatus, Spectrum and Class Licences Explained Apparatus, spectrum and class licences explained. How to tell which type covers your service, and the fork between assigned and non-assigned apparatus licences.
- What Is an ACMA Accredited Person? Frequency Assignment Certificates and What They Can Certify An accredited person is authorised under Part 5.4 of the Radiocommunications Act 1992 to issue certificates. What the two kinds certify, and what they cannot.
- The 900 MHz Band Replan: What Australia's Decision Means for IoT, Mining Radios, and Smart Meter Networks A working guide to the ACMA 900 MHz replan: the new band edges, what happens to legacy PMR, STL and telemetry, and what LoRaWAN and NB-IoT must recalculate.
- What Is Erlang? How to Size Channels and Repeaters for Radio Systems One erlang is one channel busy for a whole hour. Offered versus carried traffic, busy hour, grade of service, the Erlang B formula and when to use Erlang C.
- What Is RF Interference and Why It’s Getting Worse RF interference is spreading as wireless systems multiply and spectrum congests. What causes it, why it is worsening, and what engineers can do to mitigate it.