Blog

OTA DTv The Decibels (dB) Scale

The decibels (dB) scale is more convenient than a linear scale when dealing with signal loss or gain (dB), or power (dBm).

dB - Decibel

Signal loss or gain is commonly measured in power decibels (dB), and is the power ratio of watts out / watts in, on a base 10 logarithmic scale. Minus three decibels (-3 dB) has a power ratio of about half, plus three decibels (3 dB) is almost double power. Signal loss is a negative (-) dB, signal gain is a positive (+) dB, 0 dB is no loss or gain (a ratio of 1/1).

dB = 10 log10(ratio)
ratio = 10dB/10
ratio = Pout / Pin
Pout = Output signal power in watts.
Pin = Input signal power in watts.
Convert dB to/from Ratio

Convert dB's and ratio



Sponsored links

dBm - Signal Power

Signal power is commonly measured in watts or dBm. A dBm is decibels above (+) or below (-) one milliwatt (1 mW). A negative dBm is dB's below a milliwatt, a positive dBm is dB's above a milliwatt, 0 dBm = 1 mW.

Television broadcast signals are typically between 10 kW and 1000 kW, but can be as low as 0.001 kW ((1 Watt). Receivable signals are typically -65 dBm to as high as -5 dBm.

SIGNAL POWER
Broadcast 1000 kW = 90 dBm
100 kW = 80 dBm
10 kW = 70 dBm
1 kW = 60 dBm
100 W = 0.1 kW = 50 dBm
10 W = 0.01 kW = 40 dBm
1 W = 0.001 kW = 30 dBm
1 mW = 0 dBm
Receive 316 µW = -5 dBm
Typical Minimum 0.0003 µW = -65 dBm
Low S/N 0.00001 µW = -80 dBm
Noise Floor 2.5 x 10-8 µW = -106 dBm

CONVERSIONS
dBm = 10 log10 (mW)
mW = 10(dBm/10)

dBm to Watts
dBm

dBm
to watts

Watts to dbm

watts
to dBm


dBm - decibels above or below 1 mW
µW - microwatts = 0.000 001 W
mW - milliwatts = 0.001 W
W - watts = 1 W
kW - kilowatts = 1000 W

otadtv.com OTA DTv
The Decibels (dB) Scale