dBW
Understanding dBW
dBW provides a natural power scale for systems dealing with watts and kilowatts. While dBm is standard for circuit-level RF (where signals are milliwatts), dBW is preferred for satellite communications and broadcast where powers are in the watt-to-kilowatt range.
dBW in Link Budgets
Satellite link budgets traditionally use dBW because transmitter powers and EIRP values are conveniently expressed: a 10-watt BUC is +10 dBW; a 50 dBi antenna with 10 watts gives 60 dBW EIRP. This avoids the larger numbers that dBm would require (+40 dBm, +90 dBm EIRP).
Common Values
| Power | dBW | dBm |
|---|---|---|
| 1 mW | -30 | 0 |
| 1 W | 0 | +30 |
| 10 W | +10 | +40 |
| 100 W | +20 | +50 |
| 1 kW | +30 | +60 |
dBW = dBm - 30
EIRP (dBW) = P_TX (dBW) + G_ant (dBi)
Example satellite EIRP:
P_TX = 10W = +10 dBW
G_ant = 50 dBi
EIRP = 60 dBW = 90 dBm
Frequently Asked Questions
What is dBW?
dBW is decibels referenced to 1 watt. 0 dBW = 1 W. It is used in satellite and high-power link budgets. Conversion to dBm: dBm = dBW + 30. Conversion to watts: P(W) = 10^(dBW/10).
When should I use dBW instead of dBm?
Use dBW for satellite link budgets, broadcast transmitter power, and any calculation where powers are naturally in watts or kilowatts. Use dBm for circuit-level signals, sensitivity specifications, and test equipment measurements. Both are equivalent; the choice is convention.
How do you convert dBW to dBm?
dBm = dBW + 30. This is because 1 watt = 1000 milliwatts = 30 dB above 1 milliwatt. So +10 dBW = +40 dBm = 10 watts.