5 Common Spectrum Analyzer Mistakes (and How to Avoid Them)

5 Common Spectrum Analyzer Mistakes (and How to Avoid Them)

Small setup errors can ruin big measurements. Use these practical tips to get clean spectra and repeatable results — featuring UNI-T UTS5000A, UTS3000A, and UTS3000T+ series.

Estimated reading time: 7 minutes



Frequency → Amplitude (dBm)
Signal peaks Noise floor Average baseline Masked region
Figure 1 — Typical spectrum with narrow-band peaks and noise floor. Red area marks a masked/limit region.

What you’ll learn

  1. RBW left on auto
  2. Ignoring noise floor & dynamic range
  3. Wrong reference level & attenuation
  4. Skipping the tracking generator
  5. No warm-up or calibration

Mistake 1 Leaving Resolution Bandwidth (RBW) on Auto

Problem: Auto RBW can blur narrow signals or make sweeps unnecessarily slow.

Fix: Start wide to discover activity, then narrow RBW for selectivity. Balance sweep time vs. resolution. UTS5000A provides 1 Hz–3 MHz RBW control up to 26.5 GHz.



Frequency → Amplitude Wide RBW Narrow RBW
Figure 2 — Wide RBW (left) smears a narrow-band signal; narrow RBW (right) resolves it cleanly.
  • Scan fast, then refine: Use wide RBW to find signals; narrow RBW for final measurements.
  • Link VBW to RBW: Set VBW ≈ (0.1–1)×RBW for stable traces without over-smoothing.
  • Use averaging when RBW is narrow to improve repeatability.

Mistake 2 Ignoring Noise Floor & Dynamic Range

Problem: Weak signals disappear if DANL is high or phase noise masks nearby tones.

Fix: Check DANL/phase noise, enable preamp/averaging if available, narrow RBW, and optimize reference level. UTS3000A achieves −165 dBm DANL and ~−102 dBc/Hz @ 10 kHz.



Frequency → Amplitude Weak tone Weak tone
DANL baseline Detected weak tones
Figure 3 — Lower DANL reveals emissions previously buried in noise.
  • Lower reference level until the signal is ~5–10 dB above the noise.
  • Use Preamp/Average: If available, enable a preamp and turn on trace averaging.
  • Watch phase noise when measuring close-in spurs or adjacent channels.

Mistake 3 Incorrect Reference Level & Attenuation

Problem: Too high compresses signals; too low lets noise dominate. Wrong attenuation risks overload.

Fix: Start with auto attenuation, then fine-tune. Lower attenuation for weak signals (if safe), raise it for strong carriers. UTS3000T+ makes this simple via a 10.1″ touch UI.



Frequency → Amplitude Overload Correct level
Overdriven Correct level
Figure 4 — Overdriven input (left) vs properly staged reference/attenuation (right).
  • Target peak ~−10 to −20 dBm at the analyzer input to avoid compression.
  • Reduce attenuation for weak signals only if the input is safe from overload.
  • Use “Auto” then tweak: Start with auto, then fine-adjust reference level in 5 dB steps.

Mistake 4 Skipping the Tracking Generator

Problem: Characterizing filters, cables, or amplifiers without a TG misses frequency-response data.

Fix: Enable the TG and sweep across the DUT’s band. UTS3000A and UTS3000T+ include integrated TG options (40 MHz available) for quick scalar network analysis.



Frequency → Gain / Loss (dB) Passband ripple
Figure 5 — TG sweep showing insertion loss vs. frequency across a band-pass DUT.
  • Calibrate cables/adapters (normalize) before measuring frequency response.
  • Use markers at -3 dB points to auto-compute bandwidth and center frequency.
  • Average sweeps for smoother scalar measurements on noisy DUTs.

Mistake 5 Skipping Warm-up & Calibration

Problem: Measuring immediately after power-on introduces drift and amplitude errors.

Fix: Allow 15–20 minutes warm-up; schedule periodic amplitude/frequency calibration. UTS5000A stabilizes quickly for consistent, lab-grade accuracy.



Time → Drift Cold Warm + Cal
Cold start After warm-up/cal
Figure 6 — After warm-up/calibration (green), drift is reduced vs. a cold start (gold).
  • Warm-up 15–20 minutes before critical measurements (longer for tight specs).
  • Schedule quarterly calibration or per your QA plan; log offsets in a lab notebook.
  • Use internal reference or GPS-disciplined clock when frequency accuracy is critical.

Choose the Right UNI-T Spectrum Analyzer

Series Key Highlights Ideal For
UTS5000A Up to 26.5 GHz, RBW 1 Hz–3 MHz, phase noise ~−107 dBc/Hz @ 10 kHz, 15.6″ touch. Advanced RF/microwave, 5G/Radar R&D, tight selectivity.
UTS3000A Up to 8.4 GHz, −165 dBm DANL, ~−102 dBc/Hz phase noise, optional 40 MHz TG. EMI pre-compliance, RF component tests, general lab work.
UTS3000T+ 10.1″ touch UI, up to 8.4 GHz, RBW 1 Hz–3 MHz, −161 dBm DANL. Education, prototyping, fast RF troubleshooting.

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