Finally, it appears that gpsctl send commands to the GPS but dont feed back any info to know if the command was issued correctly or not, but finally, looking to the response in precision of the GPS itself, it appears that the commands are executed correctly.
One more thing, ¿Where can i read the gpsd-users mail list?, now i am waiting for the daily digest but i see that others appears to read it somewhere.
Thanks in advance, and sorry, i am really novice with Linux and GPS too.