dBm, watts and S-units
Convert between power, level and voltage into 50 Ω: fill in one field and the others follow. Plus the S-unit the S-meter should show on HF.
dBm, watts and S-units
One value is enough. On HF, S9 is 50 µV into 50 Ω, so −73 dBm. One S-unit is 6 dB, above that you count in dB over S9.
How the page calculates
- dBm = 10 · log10(P / 1 mW), dBW = dBm − 30
- U = √(P · 50 Ω)
- S9 = −73 dBm (50 µV into 50 Ω), one S unit = 6 dB
An example: 100 W is 50 dBm or 20 dBW, and into 50 Ω that's about 70.7 V. At the receiver, −53 dBm reads S9 + 20 dB on the S-meter.
Related terms
- S9 + 20 dB
- above S9 you keep counting in decibels, one S-unit is 6 dB
- S1 to S9
- signal strength: 1 barely perceptible, 5 fair, 9 very strong
- QRP
- reduce power, operating at low power