Microwave Link Planning
Effective isotropic radiated power from transmitter output, feeder loss, and antenna gain. Returns EIRP and ERP across dBm, watts, milliwatts, and dBW with a clear system gain breakdown for compliance, link budgets, and licence applications.
EIRP, the Effective Isotropic Radiated Power, is the single number that determines whether a transmitter system meets its regulatory limit. Most ACMA radiocommunications licence conditions are written in EIRP rather than transmitter output, because what the regulator cares about is what is actually radiated, not what comes out of the back of the radio. The same is true for ITU radio regulations and the FCC. Get EIRP wrong and the system either over engineers safety margins (overspending on smaller antennas or lower power) or under reports radiated power (creating a compliance and interference problem). The calculation is not difficult, but the conventions around feeder loss, antenna gain references (dBi versus dBd), and ERP versus EIRP catch people out.
The noIM₃ EIRP Calculator gives a precise, defensible answer in one workspace. The standard relationship EIRP equals Pt minus Lc plus Gt is implemented directly. Inputs are transmitter output power Pt in dBm, total system loss Lc in dB (cable, connector, jumper, combiner, filter), and antenna gain Gt in dBi. Output is EIRP in dBm, watts, milliwatts, and dBW simultaneously, plus the ERP equivalent (referenced to a half wave dipole, lower than EIRP by 2.15 dB) for licence frameworks that specify ERP rather than EIRP.
A full system gain breakdown shows the power at each stage. Transmitter output, power at the antenna input after feeder loss, antenna gain contribution, total system gain, and final EIRP. The breakdown supports troubleshooting (where exactly is the loss happening), optimisation (where is the highest leverage change), and documentation (which stage do you cite in the licence application). Built in presets cover WiFi access points, UHF and VHF handheld radios, cellular base stations, microwave point to point links, and LoRa node configurations so common scenarios are one click away.
Calculates Effective Isotropic Radiated Power using EIRP equals Pt minus Lc plus Gt with consistent dB arithmetic. Effective Radiated Power is also returned, referenced to a half wave dipole. ERP is lower than EIRP by 2.15 dB and is the form some regulatory frameworks specify, so both are surfaced together to remove conversion as a source of compliance error.
Power at each stage of the transmission chain is reported. Transmitter output, power at the antenna input after feeder loss, antenna gain contribution, total system gain, and final EIRP. The clear separation of stages supports troubleshooting underperforming systems, optimising the highest leverage change, and documenting transmitter compliance for licence applications.
EIRP and ERP are automatically converted across dBm, watts, milliwatts, and dBW. Useful when an ACMA licence specifies the limit in watts, an internal engineering document expects dBm, and a customer report needs the equivalent in dBW. No mental conversion required between unit families.
Total system loss Lc accepts the aggregated loss from cable runs, connector and jumper losses, combiner and duplexer insertion loss, and any filter or surge protection in the path. Output explicitly shows the power at the antenna input after losses are applied, so the impact of feeder length and component selection is visible rather than implied.
Quick select presets for WiFi 2.4 GHz and 5 GHz access points, UHF and VHF handheld radios, cellular base stations, microwave point to point links, and LoRa node configurations. Each preset populates transmitter power, typical feeder loss, and antenna gain so common feasibility questions are one click away. Manual entry remains available for unusual configurations.
Interactive scaling shows how EIRP increases with antenna gain and how feeder loss reduces radiated power. Useful for evaluating antenna upgrades, longer cable runs, or transmit power changes against an EIRP limit, and for explaining the trade off to non specialist stakeholders.
Output is structured for direct inclusion in ACMA licence applications, internal compliance documentation, and customer engineering reports. Both EIRP and ERP forms are returned alongside the system gain breakdown, so the documented chain from transmitter to radiated power is traceable end to end.
Runs entirely in your browser. No transmitter power, antenna gain, or licence content is submitted to a server. Useful for commercially confidential cellular and broadcast infrastructure work, defence and security installations, or environments where information security policy prohibits sending engineering data to third party services.
Reach for the EIRP Calculator in any of the following situations.
EIRP equals Pt minus Lc plus Gt, all in dB. Pt is transmitter output power in dBm. Lc is total system loss in dB (cable, connectors, jumpers, combiners, filters). Gt is antenna gain in dBi. The result is EIRP in dBm, with simultaneous output in watts, milliwatts, and dBW. ERP is also returned, referenced to a half wave dipole rather than an isotropic radiator, and is 2.15 dB lower than EIRP for the same configuration.
EIRP (Effective Isotropic Radiated Power) is the radiated power referenced to an ideal isotropic radiator. ERP (Effective Radiated Power) is the same physical quantity but referenced to a half wave dipole. Because a half wave dipole has 2.15 dB of gain over isotropic, ERP is 2.15 dB lower than EIRP for the same actual radiated power. Australian ACMA conditions and ITU radio regulations typically use EIRP. Some older broadcasting and amateur frameworks still use ERP. Both are surfaced together so the conversion is never a source of compliance error.
Total system loss between the transmitter output and the antenna input. This typically includes coaxial cable loss (in dB per metre at the operating frequency, multiplied by length), connector loss (typically 0.1 to 0.5 dB per connector pair), jumper losses, combiner or duplexer insertion loss, filter insertion loss, and any surge protection or lightning arrester loss. Output explicitly shows the power at the antenna input so the impact of each component is visible.
Antenna gain is expected in dBi (referenced to an isotropic radiator), which is the IEEE 145 standard definition. If your antenna datasheet quotes gain in dBd (referenced to a half wave dipole), add 2.15 dB to convert to dBi before entering. Many vendor datasheets quote dBd without saying so, and the 2.15 dB difference is the most common source of EIRP calculation errors.
ACMA radiocommunications licence conditions typically specify a maximum EIRP at the antenna for the licensed frequency. The calculator returns EIRP in the unit family the licence uses (most commonly watts), shows the system gain breakdown so the licence application can document the transmitter, feeder, and antenna chain explicitly, and supports the configuration of a regulatory limit so compliance margin in dB is reported alongside the result.
The EIRP Calculator computes the radiated power against transmitter compliance limits expressed as EIRP. The Antenna Power Density Calculator extends that to human exposure assessment, returning power density, electric field, magnetic field, and minimum safe distance against ARPANSA, ICNIRP, and FCC reference levels. Use EIRP for transmit power compliance against a licence EIRP cap. Use power density for human exposure compliance against ARPANSA and equivalent international references.
No. The calculator runs entirely in your browser. No transmitter power, antenna gain, or licence content is submitted to a server. Useful for commercially confidential cellular and broadcast infrastructure work, defence and security installations, or environments where information security policy prohibits sending engineering data to third party services.
Yes. EIRP limits are central to unlicensed band frameworks (FCC Part 15, ACMA class licences for ISM bands, RED for European deployments). The calculator handles WiFi 2.4 GHz, WiFi 5 GHz, LoRa 915 MHz, and other ISM bands directly, and the configurable regulatory limit feature lets you check compliance margin against the relevant cap at the operating frequency.
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