Further to my last...
And remember.. your aircraft transmitter is weaker than SFO Radio equipment so the RO hears you weaker than you think they do in some cases. Also, the RO is typing a format specific message into the Air Ground System which is then displayed to the Air Traffic Controller on the Ocean 21 ATC system (a sophisticated mock radar system) from which they control flight movements.
Please feel free to visit SFO ARINC (located in Livermore CA) anytime you have a layover in SFO, or NYC ARINC (located opposite Islip Long Island Airport) anytime you are in NY for a tour of either radio room. Plugging and seeing what the RO's hear and type will give you a better understanding of how it all works.