Calculator Form
Enter your RF values below. The form uses three columns on large screens, two on smaller screens, and one on mobile.
Formula Used
- Power conversion to dBm: dBm = 10 × log10(Power in mW)
- Power conversion to watts: W = 10 ^ ((dBm - 30) / 10)
- dBd to dBi conversion: dBi = dBd + 2.15
- Mismatch reflection coefficient: Γ = (VSWR - 1) / (VSWR + 1)
- Mismatch loss: -10 × log10(1 - Γ²)
- Total system loss = feedline loss + connector loss + other loss + mismatch loss
- Power at antenna input = transmitter power in dBm - total system loss
- EIRP = power at antenna input + antenna gain in dBi
- ERP = EIRP - 2.15 dB
How to Use This Calculator
- Enter the transmitter power and choose the correct unit.
- Enter antenna gain and select dBi or dBd.
- Add feedline, connector, and other system losses.
- Enter VSWR to include mismatch loss in the result.
- Press Calculate to show EIRP and ERP above the form.
- Review dBm, dBW, and watt values for documentation.
- Use the CSV or PDF buttons to save the result.
Example Data Table
| Case | Tx Power | Feedline Loss | Connector Loss | Other Loss | Gain | VSWR | EIRP | ERP |
|---|---|---|---|---|---|---|---|---|
| Base Station A | 50 W | 1.5 dB | 0.5 dB | 0.3 dB | 8.15 dBi | 1.20 | 54.4441 dBm | 52.2941 dBm |
| Telemetry Link B | 30 dBm | 1.0 dB | 0.2 dB | 0.1 dB | 6 dBd | 1.10 | 36.9374 dBm | 34.7874 dBm |
| Repeater C | 20 W | 2.2 dB | 0.4 dB | 0.5 dB | 10 dBi | 1.50 | 49.9101 dBm | 47.7601 dBm |
Antenna Gain and ERP Guide
Why antenna gain and ERP matter
Antenna gain and ERP shape every radio link plan. Small losses matter. Small gains matter too. This calculator helps engineers estimate practical radiated output fast.
Transmitters do not radiate alone. The antenna system changes final signal strength. Feedline loss reduces usable power. Connector loss also reduces power. Antenna gain then concentrates that remaining power in a preferred direction. The final result influences coverage, compliance, and link quality.
ERP and EIRP are related but different. EIRP uses isotropic gain. ERP uses dipole gain. The difference is 2.15 dB. That small value is important in technical work. It affects reporting, licensing, and design checks.
Key inputs in this calculator
Start with transmitter power. Enter it in watts, milliwatts, dBm, or dBW. Then add feedline loss, connector loss, and other system loss. You can also enter antenna gain in dBi or dBd. An optional VSWR field estimates mismatch loss. That gives a more realistic output value.
These inputs reflect real RF installations. Coaxial cable attenuation varies by length and frequency. Connectors add small but meaningful losses. High gain antennas improve directional performance. Poor matching increases reflected power. Together, these factors determine radiated performance.
What the results tell you
The tool calculates total loss first. It then finds power at the antenna input. After that, it computes EIRP and ERP. Results are shown in dBm, dBW, and watts. This helps when comparing lab values, regulatory limits, and field documentation.
A higher EIRP does not always mean a better design. Coverage goals matter. Interference control matters. Safety margins matter. Balanced system planning is usually better than chasing raw output.
Better engineering decisions
Use this calculator during RF planning, antenna replacement, cable selection, and compliance review. It is useful for wireless links, broadcast setups, telemetry systems, and industrial radio networks. It also supports quick what if checks before installation.
Reliable ERP estimates reduce guesswork. They improve documentation. They support smarter antenna system decisions. That saves time and reduces expensive field corrections later.
It helps compare regulatory limits. It helps validate upgrade paths. It helps explain system behavior clearly during review meetings.
Engineers can test several scenarios quickly. Try shorter cable runs. Try lower loss connectors. Compare dBi and dBd carefully. Clear comparisons make procurement and deployment decisions easier.
Frequently Asked Questions
1. What is ERP?
ERP is effective radiated power referenced to a half wave dipole. It equals EIRP minus 2.15 dB. Many engineering and regulatory documents use ERP for reporting.
2. What is the difference between ERP and EIRP?
EIRP uses an isotropic radiator as the reference. ERP uses a dipole reference. Because of that, ERP is always 2.15 dB lower than EIRP for the same system.
3. Why does feedline loss matter?
Feedline loss reduces the power reaching the antenna. Even a few decibels can cut radiated power significantly. That changes coverage, link budget, and compliance values.
4. Should I enter gain in dBi or dBd?
Enter whichever value your antenna datasheet provides. The calculator converts dBd to dBi automatically. This avoids reference mistakes and keeps ERP and EIRP results consistent.
5. What does VSWR change in this calculation?
VSWR adds mismatch loss. A poor match reflects some power back toward the source. Including it gives a more realistic estimate of power accepted by the antenna.
6. Can I use dBm instead of watts?
Yes. The calculator accepts watts, milliwatts, dBm, and dBW. It converts each value internally, then shows the results in all three common output formats.
7. Is a higher ERP always better?
No. Higher ERP can improve reach, but it can also increase interference and exceed design targets. The best result depends on coverage, compliance, and system balance.
8. When should I export the result?
Export after checking the final input set. Saved CSV and PDF files are useful for RF planning notes, approvals, maintenance records, and installation documentation.