TinySA Ultra First Measurement Setup

[Pavel]

Short answer: Begin with a protected input, known signal, narrow enough span and correct attenuation/reference level. A spectrum analyzer can be damaged by excessive RF power or DC, so calculate the input before connecting any transmitter.

Before you start​

• Check maximum RF input level and DC tolerance before connecting a transmitter, powered line or unknown source to test equipment.
• Warm up the instrument, use known cables and adapters, and calibrate at the connector plane where the device under test will be attached.

Step-by-step method​

1. Step 1: Check the exact TinySA model's maximum input and DC restrictions. For an unknown source, begin through a rated external attenuator and DC block where appropriate.
2. Step 2: Set center frequency and span around the expected signal, then choose reference level and internal attenuation so the peak is on-screen without clipping. Avoid maximum sensitivity until input level is known.
3. Step 3: Set resolution bandwidth narrow enough to separate nearby signals but wide enough for reasonable sweep time. Use a known generator or local signal to confirm frequency display.
4. Step 4: Measure the noise floor with the input terminated, then connect the source and record peak, span, RBW, attenuation and reference level. Repeat at a second attenuation to check compression.

Concrete example​

For a low-level 433.92 MHz test source, start with a several-megahertz span and conservative attenuation. Narrow the span only after finding the carrier. If the displayed amplitude changes unexpectedly when 10 dB more attenuation is added and compensated, the analyzer or source may be compressing.

How to judge the result​

A valid first measurement keeps the input below limits, locates the expected carrier, repeats at two safe attenuation settings and includes enough settings to reproduce the display.

What to record​

• Save frequency span, calibration state, attenuation, reference level and connector plane with every result.
• Repeat the measurement after reconnecting the device; a large change often points to a poor adapter, cable or calibration.
• Use a VNA for reflection and network measurements, and a spectrum analyzer for signal energy versus frequency.

Common mistakes​

• Changing several hardware, software or RF variables at once, which removes the controlled comparison needed to identify the cause.
• Treating one autoscaled screenshot or one unusually good result as proof without recording the settings and repeating the test.
• Connecting a handheld transmitter directly because its average power seems low ignores peak power and can exceed the analyzer input instantly.

Final check​

Reconnect the standards or device under test and repeat the measurement without changing the calibration plane. Save the span, calibration, attenuation and uncertainty with the result.