dB Explorer

A simple visual guide to decibels in Wi‑Fi, radio, antennas and cable loss.

Absolute RF signal level at the receiver input. Uses dBm.

Interpretation context ?

Signal level at receiver input ?−100 dBm

Extremely lowHigher level

Power ratio1×

MeaningWeak-signal range

What this means

−67 dBm

Strong arriving signal

This is the arriving signal level. Compare it with receiver sensitivity or noise floor to judge whether it is usable.

Signal visual

Live visual for the selected category

Antenna pattern preview

Beam narrows as gain increases

Simplified pattern — not to scale.

+3 dB ≈ 2×Power roughly doubles

+10 dB = 10×Power increases tenfold

−10 dB = 1/10Power is reduced tenfold

dBm is powerCompared with 1 mW

Quick conversions

dB change ?

Power ratio: 2.00×

dBm ?

Power: 1 mW

dBi / dBic ?

Approx dBd: 7.1 dBd

Suffix guide

The letters after dB tell you the reference. No suffix usually means relative gain or loss.

dBGeneric change. Coax loss: −2 dB

dBmActual power vs 1 mW. Wi‑Fi: −67 dBm

dBiAntenna gain vs isotropic. Common for Wi‑Fi antennas

dBdAntenna gain vs dipole

dBicCircularly polarised antenna gain

dBcCompared with a carrier

dBFSDigital full scale

SNR dBSignal versus noise

Link / signal budget check

Start power, dBm

Cable loss, dB

Antenna gain, dB

Path loss, dB

RX antenna, dB

Preamp gain, dB

Result−71.6 dBm

Reference table

Term	Use it when...	Example
`dB`	You mean a gain, loss, or ratio	Coax loss `−2 dB`
`dBm`	You mean absolute power compared with 1 mW	RX input `−100 dBm`
Sensitivity	You mean the minimum level a receiver may use	`−122 dBm` sensitivity
Noise floor	You mean background noise over a bandwidth	`−174 dBm/Hz` thermal reference
`dBi`	Antenna gain vs isotropic	Wi‑Fi antenna `5 dBi`
`dBd`	Antenna gain vs dipole	`7.1 dBd`
`dBic`	Circular satellite antenna gain	2MCP8A `9.2 dBic`

Help / formulas

Why does cable loss not use the m in dBm?

The m in dBm means the value is compared with 1 milliwatt. Cable loss is not an amount of power by itself — it is only a reduction. So cable loss is written as plain dB. If the signal starts at +30 dBm, then after −2 dB of cable loss it becomes +28 dBm.

Why is plain dB generic?

dB is a ratio. It only says how much bigger or smaller something is. The suffix tells you what it is referenced to.

Formula: dB to power ratio

power ratio = 10^(dB/10). Example: 10^(3/10) ≈ 2.

Formula: dBm to milliwatts

mW = 10^(dBm/10). So 0 dBm = 1 mW, and negative dBm values are less than 1 mW.

dBi, dBd and dBic

dBd ≈ dBi − 2.14. dBic is normally used for circularly polarised antennas. Example: 9.2 dBic ≈ 7.1 dBd.

Why does bandwidth matter for weak signals?

Thermal noise at room temperature is about −174 dBm/Hz. Wider bandwidth collects more noise: add 10 × log10(bandwidth in Hz). That is why −90 dBm can be poor for Wi‑Fi but workable in some narrowband radio examples.

Receiver sensitivity versus received signal

The RX input level is the signal arriving at the receiver. Sensitivity is the level the receiver needs for a specified mode, bandwidth and quality. Link margin is the difference between the two.