Troubleshooting (TEDS)

This topic contains information to help you troubleshoot demod measurements when using TEDS Demodulation. Review Setting up a TEDS Measurement for additional information.

Problem

Possible Cause

Solution

Demodulation fails to lock-on to signal

Signal not present.

Check test setup connections. Try a recorded signal to test your setup (File > Recall > Recall Recording).

 

Carrier too far from center frequency.

Adjust center frequency to ± 500 Hz of the carrier frequency (MeasSetup > Frequency).

 

Input signal is over-loaded or under ranged.

Adjust input range (Input > Range).

 

Frequency span is too narrow.

Increase frequency span (MeasSetup > Frequency).

 

TEDS signal spectrum is inverted.

Clear: MeasSetup > TEDS (TETRA2) Demod Properties > Format tab > Mirror Frequency Spectrum.

Message, "Sync not found."

VSA has lost synchronization symbols.

This message is typical to carrier frequency drift over a long time record and the carrier has drifted more than 100Hz from center. Check your signal input.

Message, "Pulse not found."

VSA cannot find a pulse for the slot (must be an uplink slot).

This message is typical when you input a downlink slot for analysis, but the VSA is set for an uplink slot. Check your slot parameter settings.

ADS application fails to work with TEDS demodulation

Refer to Troubleshooting ADS.

 

Constellation diagram is blank and reports PULSE NOT FOUND.

Missing input signal or incorrect slot format.

Check signal and slot format selection: MeasSetup > TEDS (TETRA2) Demod Properties > Format tab > Slot Format menu.

Constellation diagram is blank but does not report PULSE NOT FOUND.

Incorrect Y-axis scaling.

Select: Trace > Auto Scale.

Constellation diagram symbols are scrambled and do not correlate to the ideal position overlay.

Incorrect demod properties setting or input signal is bad.

Maintain current demod properties settings and switch to a matching recorded signal to verify correct operation: File > Recall > Recall Recording. If display is correct, the problem is the input signal.

If problem persists, check the following demod properties from MeasSetup > Demod Properties:

Advanced tab > Time Scale Factor = 1 (except in special circumstances).

Advanced tab > Filter Alpha = 0.2 (except in special circumstances).

Overlay of ideal symbol positions in a constellation diagram.

IQ Normalize feature not selected.

Select: MeasSetup > TEDS (TETRA2) Demod Properties > Advanced tab > IQ Normalize box.

Signal Trace for Overlaid does not show overlaid portion (in white).

Incorrect Y-axis scale, where overlaid portion requires LinMag scale.

Modify scale: Trace > Format tab > Format menu.

Signal Trace shows only a green line -or- Constellation diagram is too small.

Incorrect Y-axis scaling.

Select: Trace> Auto Scale.

Trace shows the overall signal instead of subcarriersignal -or- the Trace shows the wrong subcarrier.

Wrong Trace selection or wrong subcarrier selection.

Select your trace from: Trace > Data > Channel 1 Subcarr and then select the subcarrier from: MeasSetup > TEDS (TETRA2) Demod Properties > Analysis tab > Analysis Subcarrier menu.

See Also

Setting up a TEDS Measurement

About Option BHA: TEDS Modulation Analysis

Typical TEDS Measurements

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