The importance of the TUNE function

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IZ4PNN
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The importance of the TUNE function

Post by IZ4PNN »

If you have noticed reception problems, you probably have not performed a calibration (TUNE).

All TTGOs are shifted in frequency, some even by several KHz.

To improve the sensitivity of the MySondy GO for the RS41, the default RX band has been narrowed to 3100 Hz, in previous versions it was 6300 Hz.

One way to receive RS41 correctly is to set the RX band to 6300 Hz.

If, on the other hand, you want to obtain maximum sensitivity, set the RX band of the RS41 to 3100 Hz and proceed with the calibration (TUNE).

Let's make sure we have a strong signal from an RS41 nearby.
In the MySondy GO App we set the radiosonde type on RS41 and set the frequency to the nominal frequency of the RS41 that is transmitting.
At this point we go to the TTGO settings and press the TUNE button.
In a few seconds MySondy GO will find the shift in frequency, press SAVE.

If we don't have a strong signal from an RS41, we can do a manual calibration:

in the MySondy GO App we go to the TTGO settings.
We insert the offset value in the OFFSET field and press SAVE.
This value must bring the value written in brackets (AFC) to almost 0 when receiving a radiosonde.
In the example below we see in brackets an AFC of +3951 Hz. It means that MySondy GO is able to center the signal by moving +3951 Hz with respect to the set frequency.
We will therefore have to set the OFFSET field to 3950/3951 to bring the value in brackets (AFC) closer to 0.
If the value in brackets (AFC) when receiving a signal is close to 0 (0-200 Hz) then our MySondy Go is correctly calibrated.

Calibration is usually performed with an RS41 but is valid for all radiosonde models.

Some TTGOs may have problems receiving RS41 with RX band at 3100 Hz even after having done the calibration. In this case, gradually increase the RX band (ex. 3900 Hz) until you find the best value.

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Mirko Dalmonte (IZ4PNN)
MySondy Developers Team
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