EIRP Calculator
Calculate Effective Isotropic Radiated Power for RF and telecommunications systems
Calculate EIRP (Effective Isotropic Radiated Power)
Power output from the transmitter
Directional gain of the antenna
EIRP Calculation Results
Formula used: EIRP = Tx - Lc - Lconnectors + Ga
Calculation: 21 - 3 - 1 + 11 = 28 dBmW
ERP (vs dipole): 25.85 dBmW
Regulatory Compliance (FCC)
Example Calculation
WiFi Access Point Setup
Transmitter power: 21 dBmW (125.9 mW)
Cable loss: 3 dB (RG-58 coax, 10m at 2.4 GHz)
Connector loss: 1 dB (2 connectors × 0.5 dB each)
Antenna gain: 11 dBi (directional antenna)
EIRP calculation: 21 - 3 - 1 + 11 = 28 dBmW
Result: 28 dBmW (631 mW) EIRP
Ham Radio Setup
Transmitter: 30 dBmW (1W)
Feedline: LMR-400, 20m at 144 MHz = 1.32 dB loss
Antenna: Yagi with 15 dBi gain
EIRP: 30 - 1.32 + 15 = 43.68 dBmW (23.3W)
EIRP Applications
License Compliance
Meeting regulatory power limits
Link Budget
RF system performance analysis
Coverage Planning
Wireless network design
Interference Analysis
EMC and coexistence studies
Key RF Concepts
EIRP: Power radiated by equivalent isotropic antenna
dB Scale: Logarithmic power and gain measurements
Antenna Gain: Directional concentration of RF energy
Cable Loss: Power lost in transmission lines
Connector Loss: Power lost at RF connections
Understanding EIRP (Effective Isotropic Radiated Power)
What is EIRP?
EIRP is the amount of power that a theoretical isotropic antenna (radiating equally in all directions) would need to produce the same signal strength in the direction of maximum gain of an actual antenna. It's a key parameter in RF system design and regulatory compliance.
Why is EIRP Important?
- •Regulatory compliance for RF equipment
- •Link budget calculations
- •Interference analysis and coordination
- •Coverage area planning
EIRP Formula
EIRP = Tx - Lc - Lconnectors + Ga
(All values in dB scale)
- Tx: Transmitter output power (dBmW)
- Lc: Cable loss (dB)
- Lconnectors: Connector losses (dB)
- Ga: Antenna gain (dBi)
dBi vs dBd: dBi = dBd + 2.15
dBi compares to isotropic, dBd to dipole antenna
EIRP vs ERP
EIRP uses isotropic antenna reference (dBi)
ERP uses dipole antenna reference (dBd)
ERP = EIRP - 2.15 dB
dBmW to Watts Conversion
| dBmW | Watts | dBmW | Watts | dBmW | Watts |
|---|---|---|---|---|---|
| -30 | 0.000001 | 0 | 0.001 | 30 | 1 |
| -20 | 0.00001 | 10 | 0.01 | 40 | 10 |
| -10 | 0.0001 | 20 | 0.1 | 50 | 100 |
| -3 | 0.0005 | 23 | 0.2 | 53 | 200 |
| 0 | 0.001 | 27 | 0.5 | 57 | 500 |
Common Cable Types and Losses
Low-Loss Cables (dB/100m at 2.4 GHz)
- • LMR-600: 8.2 dB/100m
- • LMR-400: 10.8 dB/100m
- • Heliax 1/2": 3.3 dB/100m
- • RG-213: 16.4 dB/100m
Standard Cables (dB/100m at 2.4 GHz)
- • RG-58: 32.5 dB/100m
- • RG-6 (75Ω): 24.6 dB/100m
- • RG-8: 16.4 dB/100m