Audio Systems: connecting satellite to surround sound, digital satellite receiver, digital audio signal

Question
I just purchased a plasma HDTV and want to connect my satellite receiver to my Yamaha Home Theater System which is approximately 8 years old. My satellite receiver is connected in the following manner: RF coaxal in from satellite dish, RF coaxal in from roof antenna then out to TV (coaxal in). I connected the A/V cables of the satellite receiver to the AV-1 ports of the TV but I was unable to connect the component cables because the satellite receiver does not have them. I have an optical digital cable connected to the TV digital (out) and to the digital (in) port of the home theater. There are no digital out ports on the satellite receiver. The only port on the receiver that is not in use is for s-video which is not connected at this time. These connections give me digital audio on my local digital channels that I get from from my roof antenna, but I don't have digital audio on the satellite channels. After reading other related articles I'm guessing that in order to get digital audio it will require that I upgrade my satellite receiver to one that provides the appropriate digital out connections that I can connect directly to the surround sound. But, I'm still confused as to why I am receiving digital audio signal on my local channels and not the satellite channels. Is the coaxal from my satellite to the TV capable of transmitting digital audio and, if so, why isn't it transmitting the satellite channels?  Thanks for any help.

Answer
You're getting the digital reception on your local channels from the roof antenna, as those are transmitted through the air like any other signal. To get digital sound from the satellite, you'll have to have a digital satellite receiver, and it sounds like you do not. If there isn't a digital audio out on the satellite box, you'll never get digital audio from it.

The coaxial cable is fully capable of carrying the signal required for digital surround, you basically will have to get a digital satellite receiver to decode the surround audio.