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venerdì 31 gennaio 2020

Lack of Stereo Pilot and RDS synchronization checked with Elenos Signal Predator

While playing around the FM band with the Elenos Signal Predator I was captured from a strange behaviour of a station .
The RDS BPSK constellation of the RDS signal looked similar to the " dance of black holes " before merging and generating gravitational waves .
This shows that there is no synchronization between the stereo Pilot at 19 kHz and the suppressed carrier at 57 kHz of the RDS .
Some one could ask "  why this is needed , or convenient ?" 
The answer is , because in this case , it is possible to minimize the sum of the Pilot and RDS peak modulation , to leave more room to the audio modulation and stay into the constraint of +/- 75 KHz .
Another advantage is that also the intermodulation between the RDS modulation and the MPX signal is minimized .
In this video you can look at the strange constellation " dance " when the Pilot and RDS are not synchronized .
The first 60 s is the station with lack of synchronization . The other 20  is a station with correct synchronization .The rest is again the station with lack of synchronization .
I remember in the past to have seen the same station correctly synchronized .
I would say that for some reason something is not working now correctly .
Nobody will claim that there is a problem because on the audio there is not perceptible degradation , but Signal Predator is able to easily show this kind of problem .




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