> ## Documentation Index
> Fetch the complete documentation index at: https://docs.solidyne.ar/llms.txt
> Use this file to discover all available pages before exploring further.

# Tuner and Measurements

> FM Tuner and Transmission Monitoring

## 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.

<Warning>
  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.
</Warning>

### 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.

### 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).

***

### DIAL SCAN

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

<img src="https://mintcdn.com/solidyne/a7lu0Xpt375mm9I5/images/542/542-DIAL_SCAN.png?fit=max&auto=format&n=a7lu0Xpt375mm9I5&q=85&s=8d3172b32860f5b5359fdb008f96e20d" alt="542 DIAL SCAN Pn" width="1680" height="519" data-path="images/542/542-DIAL_SCAN.png" />

***

## Transmission Analysis

### FM Measurements

Monitoring of parameters measured on the tuned signal:

<img src="https://mintcdn.com/solidyne/a7lu0Xpt375mm9I5/images/542/542-FM_ANALYZER.png?fit=max&auto=format&n=a7lu0Xpt375mm9I5&q=85&s=76f4690fad2243b8857fd0694fde6836" alt="542 FM ANALYZER Pn" width="1857" height="451" data-path="images/542/542-FM_ANALYZER.png" />

* **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

    <Note>
      Appropriate integration depends on regional standards.
    </Note>
* **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.

***

### Channel Separation, Distortion and SNR

The system measures:

* Channel separation.
* Total harmonic distortion + noise (THD+N).
* Signal-to-noise ratio (SNR).

<img src="https://mintcdn.com/solidyne/a7lu0Xpt375mm9I5/images/542/542-FM_measurrements.png?fit=max&auto=format&n=a7lu0Xpt375mm9I5&q=85&s=ff60a7051beffca0da8b60818d03292a" alt="542 FM Measurrements Pn" width="1644" height="321" data-path="images/542/542-FM_measurrements.png" />

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 dB**   | **Excellent** |
|   35 to 40 dB   |   Very good   |
|   30 to 35 dB   |      Good     |
|   25 to 30 dB   |      Fair     |
|     \< 25 dB    |      Poor     |

<Info>
  Separation can be optimized from the stereo encoder advanced controls.\
  See **Channel Separation Measurement and Adjustment**.
</Info>

***

### 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.

<Warning>
  The report introduces **brief audible tones on-air** during measurements.
</Warning>