📊 dB on a Spectrum Analyzer

A signal that looks only a little lower on the screen can be a thousand times weaker — because the analyzer’s vertical scale is in decibels, not a straight line. This trainer teaches you to read those levels the way a field tech does: place markers to measure the gap between two signals in dB, turn that gap into what it really means in power and voltage, then practice with random gaps and real bench scenarios until it’s instinct.

The analyzer screen

Vertical axis: amplitude in dBm, 0 at the top down to −120 at the bottom, one division every 10 dB. Tap or click anywhere on the screen to place a marker — it snaps to a nearby peak. The two markers (M1, M2) measure each signal’s level and the delta (the gap) between them.

signal peaks noise floor (~−100 dBm) Marker 1 Marker 2
Marker 1
tap the screen to place
Marker 2
tap again to place
Δ Delta (M1 − M2)
the gap between the two signals
Each horizontal line is 10 dB. Try the carrier (−30 dBm) and the harmonic (−55 dBm) — that 25 dB gap means far more than it looks, which is what the translation below shows.

Real-world scenarios

These are the situations a tech actually faces on a service monitor. Each one loads onto the screen above and poses the question you’d ask on the bench — then shows you how to reason it out.

Predict-first practice

Reading levels is a skill you build by guessing before you check. Hit “Quiz me” for a random gap, predict the power and voltage ratios, then see how close you were. This is where the instinct gets wired in.

What that gap actually means

A dB difference is a ratio in disguise. Here's what the gap between your two markers translates to in real power and voltage — and why the numbers are so different from how the screen looks.

Place both markers on the screen above to see the translation. Try the “Markers on both peaks” button for the carrier-vs-harmonic example.