Minimum Signal

A television minimum signal varies with model and mainly depends on the TV receiver minimum Signal-to-Noise (S/N) ratio, and its Noise Figure (NF). The NF is the noise the receiver introduces to the input signal. The lower the minimum S/N and the lower the NF, the lower the minimum signal needs to be. Signal power is measured on a base 10 logarithmic scale in dBm -- decibels (dB's) above or below 1 milliwatt.

TV Receiver Dynamic Range

Televisions will process signal power levels between a high of - 5 dBm to around -65 dBm. Above -5 dBm the receiver is overwhelmed and distorts the signal so it cannot be processed. The required minimum broadcast signal mainly depends on local conditions (electronic noise pollution and power line distortions), and the receiver sensitivity (mainly S/N and NF). Under ideal conditions (TV antenna ≥ 30 feet high, no electronic pollution and clean power, and a highly sensitive receiver) a TV might get a -80 dBm signal. Most televisions and conditions will require a minimum signal around -65 dBm.

Bars Power (dBm) Percent
4 bars Strong -30 to -5 58 - 100%
3 bars Good -45 to -30 33 - 58%
2 bars Normal -55 to -45 17 - 33%
1 bars Minimal -65 to -55 0 - 17%
0 bars Low S/N < -65

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Television receivers typically have a noise figure of 10 dB, but it can be as low as 6 dB, to as high as 15 dB or more. Minimum signal-to-noise is typically 30 dB depending on television and interference from other signals, multi-path, electronic noise, and power source. A TV receiver will typically have a minimum S/N of 25 to 30 dB specification, some claim as low as 20 dB.

Specification Typical Variation
Noise Figure (NF) 10 dB 6 to 15 dB
Signal-to-Noise (S/N) 30 dB 20 to 35 dB

Another factor is background noise, also called thermal or kTB noise, and is based on receiver noise bandwidth (6 MHz for a TV RF channel), and temperature. Temperature has a minor effect, and it is standard practice to use 300°K (80°F / 27°C), or 290°K (62°F / 17°C) for calculations. Noise is random with an average deviation of about ± 5 to ± 10 dB from the average level.


Most TV's and locations will
require a signal of ≥ -65 dBm.

Pmin = kTB (NF) (S/N)
Pmin = Minimum Signal (watts).
k = Boltzmann's Constant
= 1.380 622 x 10-23 (Watt sec / °K).
T = Temperature in Degrees Kelvin (°K).
B = Receiver Noise Bandwidth in Hertz (Hz).
= 6,000,000 Hz (6 MHz) for a TV RF channel.
NF - Noise Figure (ratio).
S/N - Minimum Signal-to-Noise (ratio).

kTB Noise (80°F)
Bandwidth Noise
1 Hz -174 dBm
6 MHz -106 dBm
Estimate TV Minimum Signal
Noise Figure (NF): dB
Signal-to-Noise (S/N): dB
Bandwidth (B): MHz
Temperature (T):


Noise Floor (kTB)
+ Noise Factor (NF)
= Noise out of Receiver (kTB NF)
+ Minimum Signal-to-Noise:

Minimum TV Signal (dBm)

Television Minimum Signal