Spectrum analyzer spec sheets can look even scarier than oscilloscope specs. Instead of time and voltage, you’re suddenly dealing with frequency spans, RBW, noise floors, and phase noise. The good news is that, just like oscilloscopes, only a few specifications really matter for most users.
This guide explains spectrum analyzer specifications in simple, practical terms, without RF theory overload.
Table of Contents
What a Spectrum Analyzer Really Does
A spectrum analyzer shows signal power versus frequency.
- Horizontal axis = frequency
- Vertical axis = signal level (usually dBm)
Instead of seeing when a signal changes (like an oscilloscope), you see what frequencies exist and how strong they are.
Spectrum analyzers answer questions like:
- What frequencies are present?
- How strong is each signal?
- Is there interference?
- How wide is my signal?
Frequency Range (Start–Stop or Max Frequency)
This tells you what frequencies the analyzer can see.
Examples:
- 9 kHz – 1.5 GHz
- 100 kHz – 3 GHz
- 10 MHz – 6 GHz
Important detail:
- The maximum frequency is the headline number
- The minimum frequency matters for audio, power supplies, and low-frequency noise
Takeaway
Choose a frequency range that comfortably exceeds your highest signal of interest. For example:
- HF/VHF work → 1–2 GHz is plenty
- Cellular, Wi-Fi, GPS → 3–6 GHz needed
Resolution Bandwidth (RBW): How Close Signals Can Be Separated
RBW is one of the most important specs.
It defines:
- How close two signals can be and still appear as separate peaks
- How much noise is averaged into each measurement
Think of RBW like a sieve:
- Wide RBW → fast but blurry
- Narrow RBW → slow but detailed
Examples:
- 1 MHz RBW → fast scanning
- 10 kHz RBW → decent detail
- 100 Hz RBW → excellent detail, very slow
Takeaway
Smaller RBW = better frequency resolution, but slower sweeps.
Video Bandwidth (VBW): Display Smoothing
VBW is a post-processing filter applied after RBW.
- Lower VBW smooths noise on the screen
- Does not improve actual resolution
- Helps readability
If RBW defines measurement quality, VBW defines visual comfort.
Takeaway
Use VBW to make traces easier to read, not to improve accuracy.
Noise Floor (Displayed Average Noise Level)
The noise floor is the lowest signal level you can see.
It depends on:
- RBW
- Input attenuation
- Preamplifier settings
Lower (more negative) is better:
- −90 dBm → noisy
- −120 dBm → good
- −150 dBm → excellent
Why this matters:
- Weak signals disappear into noise
- Interference hunting requires low noise floors
Takeaway
A low noise floor matters more than max frequency for many applications.
Dynamic Range: Strong and Weak Signals Together
Dynamic range describes how well the analyzer handles strong and weak signals at the same time.
Poor dynamic range means:
- Strong signals mask weaker ones
- Intermodulation products appear
This is critical when:
- Measuring harmonics
- Looking for spurs near strong carriers
Takeaway
Good dynamic range is essential for real-world RF environments.
Input Attenuation
Input attenuation protects the analyzer and affects accuracy.
- Too little attenuation → overload and distortion
- Too much attenuation → raised noise floor
Many analyzers automatically adjust attenuation.
Takeaway
Automatic attenuation is fine for beginners. Manual control helps advanced users.
Phase Noise: Signal Purity
Phase noise describes frequency instability close to the carrier.
Low phase noise is important for:
- Oscillator testing
- Communications systems
- Measuring close-in spurs
For basic spectrum viewing:
- Phase noise is rarely critical
Takeaway
Only worry about phase noise if you work with RF sources or radios.
Sweep Time: How Fast the Analyzer Scans
Sweep time is how long it takes to scan the selected frequency range.
Affected by:
- Frequency span
- RBW (smaller = slower)
- VBW
Narrow spans + narrow RBW = slow sweeps.
Takeaway
Speed and resolution trade off against each other.
Amplitude Accuracy (dB)
This tells you how accurate the signal level measurement is.
Typical values:
- ±1.5 dB (budget)
- ±1.0 dB (good)
- ±0.5 dB (excellent)
For most hobbyists:
- Relative measurements matter more than absolute accuracy
Takeaway
Consistency matters more than perfect calibration.
Markers and Measurement Functions
Markers let you:
- Read exact frequency and level
- Measure delta between two points
- Calculate bandwidth, channel power, ACPR
These features improve usability, not raw performance.
Takeaway
Good marker tools save time and reduce mistakes.
Real-Time vs Swept Spectrum Analyzers
Swept analyzers (most budget units):
- Scan frequencies sequentially
- Can miss short-duration signals
Real-time analyzers:
- Capture everything in a wide span at once
- Much more expensive
Takeaway
Swept analyzers are fine unless you chase transient interference.
Common Marketing Traps
- “Huge frequency range” → useless without good RBW
- “Ultra-fast sweep” → meaningless without context
- “Professional RF analyzer” → marketing term
- “Software-defined” → implementation matters more than buzzwords
A Simple Buying Checklist
Ask yourself:
- What is the highest frequency I need?
- Do I care more about weak signals or wide scans?
- Will I measure harmonics or just find signals?
- Do I need portability?
For most users:
- Frequency range comfortably above target signals
- RBW down to at least 1 kHz (better if 100 Hz)
- Reasonable noise floor
- Marker and basic measurement tools
Final Thoughts
Spectrum analyzers look complex, but the core ideas are simple.
Focus on:
- Frequency range
- Resolution bandwidth (RBW)
- Noise floor
- Dynamic range
Everything else supports those fundamentals.
Once you understand these basics, spectrum analyzer spec sheets stop being intimidating and start telling you exactly what the instrument can, and can’t, do.
