Practical takeaway
dB is everywhere in Amateur Radio: amplifier gain, feed-line loss, attenuators and antenna specifications. The number describes a ratio, not a fixed number of watts.
Electricity & Electronics · Applied lab
Decibels without the headache
A decibel describes a ratio. Change a dB gain or loss and watch what happens to power in a radio signal chain.
TECHNICIAN + GENERAL SUPPORTApplied lab
Useful numbers to remember
For power ratios, +3 dB ≈ 2×, −3 dB ≈ ½, +10 dB = 10×, and −10 dB = 1/10. Those anchors solve a surprising number of radio problems.
Think in ratios first
3 dB is the doubling/halving landmark.
A gain of about 3 dB doubles power. A loss of about 3 dB cuts power in half. Exact doubling is about 3.01 dB; 3 dB is the useful mental shortcut.
10 dB moves power by a factor of ten.
+10 dB multiplies power by 10. −10 dB divides power by 10. Twenty or thirty dB simply extend that same ratio idea.
Stack the landmarks — or overshoot and come back.
You are not limited to neat 3 dB or 10 dB answers. Combine the landmarks. For example, +13 dB = +10 +3, while +17 dB = +20 −3. That second trick is often faster: go to an easy number, then come back.
Signs tell you the direction.
Positive dB means gain. Negative dB means loss or attenuation. Zero dB means the two power levels are equal.
Why hams care
You will see dB in transmitter chains, amplifiers, coax loss, filters and attenuators. Antenna gain is also expressed in dB, although an antenna redirects energy rather than creating extra transmitter power.
The STEMulation uses the exact formula. The 3 dB and 10 dB rules are the fast mental landmarks.
STEMulation
Change the dB and watch the power
How to use it: choose an input power, then move the dB control or try one of the familiar presets. Compare the exact result with the mental shortcut.
Input
Change
Power ratio
Output
Input power
GAINdB stage
Output power
Build it in your head