User:AtLaTC/sandbox

SMMS
Transmission method for RDS - Radio Data System

Single Modulation-type Multiple Subcarriers
This patented technology allows the stacking of identical generated subcarriers of 57 kHz in the range between 60 and 100 kHz in the FM multiplex.

The extra RDS2 carriers are frequency shifted in the upper empty part of the multiplex spectrum. For the commercial RDS, the subcarriers –data streams- are “stacked” in the frequency ranges that are tolerated by the ITU for additional Information (subcarriers up to 76 kHz). FCC tolerates subcarriers until 100 kHz. We speak therefore about an FM-Stack. The fact that the streams are generated uniformly allows that these can be moved to any desired frequencies and can still be decoded uniformly after re-moving. It is also irrelevant how many carriers will be used. For the standard RDS are 4.8 kHz provided. Advanced DSP technologies can work more selective, so 4.75 kHz are sufficient which corresponds to the 1/4 pilot (19 kHz). This means that all frequencies remains derivable from the pilot and therefore are theoretically 12 RDS carrier in the system conceivable. The limitation is effected by the deviation. ITU gives 20% for Pilot + Data. Because you don't need so much for the pilot, you can without losses slightly increase the data.