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FM Tuner

The internal FM tuner enables measurements of the received radio signal.
Access it from the SETUP side menu, under FM RECEIVER – ANALYZER.
  • Usually the tuned station is the same one where the processor operates.
  • Any other station can also be tuned to view its parameters.
The tuner is linked to a modulation monitor that displays different aspects of the transmission in real-time by analyzing the received RF signal.
Measurements are only valid when the station is properly tuned.
  • If RF level is below 40 dB or multipath exceeds 10%, measurements are not valid.
  • Under these conditions, data fields appear dimmed.

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Tuner Controls

  • ON/OFF → turns the FM tuner on or off.
    If reception is very poor, the unit turns off automatically.
  • FREQ → enter the station frequency (MHz, use decimal point, e.g. 95.9).
    • Type the value using the keyboard and confirm with ENTER.
    • If it was off, the tuner turns on.

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Reception Parameters

  • Reception Quality: Reception validity indicators:
    • Show if signal quality allows reliable measurements.
    • Otherwise, out-of-range variables are displayed: RF low level, Multipath, Noise, Adjacent channel interference.
  • Reception quality depends on the connected antenna.
    (See FM Receiver Antenna section).
  • RF LEVEL → RF signal level at antenna. Must be > 40 dB.
  • Multipath → distortion percentage due to reflections. Must be < 10%.
  • Band Type → FM band type according to region.
  • RBDS Mode → activates RBDS system (RDS version used in USA).

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DIAL SCAN

Tool that scans the FM band in 100 kHz steps and generates a graph showing signal strength for each detected station. 542 DIAL SCAN Pn

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Transmission Analysis

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FM Measurements

Monitoring of parameters measured on the tuned signal: 542 FM ANALYZER Pn
  • TOTAL MODULATION → FM modulation level measured on the tuned signal.
  • MODULATION MEASUREMENT RESPONSE → measurement integration time:
    • Instantaneous
    • 125 µs (recommended for peak)
    • 250 µs
    • 500 µs
    • 1 ms
      Appropriate integration depends on regional standards.
  • PILOT → pilot tone modulation % (default: 9%).
  • RDS → RDS subcarrier modulation % (default: 4%).
  • AUDIO L/R → audio level (dBFS).
  • CARRIER OFFSET → carrier deviation (kHz).
  • RDS BER (bit error ratio) → RDS data quality.
    • 0% = no errors.
    • 100% = unreadable data.
  • RDS DATA → RDS transmitted texts.

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Channel Separation, Distortion and SNR

The system measures:
  • Channel separation.
  • Total harmonic distortion + noise (THD+N).
  • Signal-to-noise ratio (SNR).
542 FM Measurrements Pn These measurements consider the complete chain: processor + stereo encoder + transmitter + antenna.
  • Can be done remotely without interrupting transmission.
  • During the process:
    • A very brief audible tone is injected (~250 ms).
    • For SNR, the on-air signal is muted for 2 seconds.
Procedure
  • Click the RUN new measurement option shown to the right of the parameter.
  • This executes the measurement for that parameter and displays the result.
Channel Separation Scale
Separation (dB)Rating
> 40 dBExcellent
35 to 40 dBVery good
30 to 35 dBGood
25 to 30 dBFair
< 25 dBPoor
Separation can be optimized from the stereo encoder advanced controls.
See Channel Separation Measurement and Adjustment.

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Technical Transmission Report

  • The DOWNLOAD FULL TEST button runs all measurements and generates a text file with results, including FM Analyzer values.
  • The file is saved to the browser’s downloads folder.
  • This report can be sent to Technical Support for remote diagnosis.
  • If the tuner is off, reports cannot be generated. To turn it on: press ON/OFF and wait for values to stabilize.
The report introduces brief audible tones on-air during measurements.