On Mon, 11 Jul 2005 13:39:23 -0500, Dan wrote:

> On Sun, 10 Jul 2005 21:11:48 -0400, General Schvantzkoph
> > wrote:
>
>>The Sirius satellite radio on my 300C has a hard time hanging onto a
>>signal when I'm on a regular tree lined street. It's mostly OK on
>>highways, although I've occasionally experienced a dropped signal on a
>>highway also, but it's terrible if there are any trees around. Is this a
>>fact of life with satellite radio or do I have a loose antenna connection?
>>Microwaves are easily blocked, especially by wet leaves, so it's possible
>>that this is normal. Are there any other 300 owners who have Sirius
>>radios, how well does it work for you? BTW I'm in Massachusetts, I don't
>>know where Sirius hangs their satellites but I wouldn't be surprised if
>>they are positioned over the middle of the country which would contribute
>>to the weakness of the signal on the coasts.
>>
> The satellite signal is literally line of sight. If you could "see"
> the satellite like a star in the sky, anywhere your antenna can not
> "see" the star there is no reception. That's why there is no
> reception in tunnels, under the awning at the gas station, in your
> garage or carport, etc. That's the only downside I've found regarding
> satellite radio, so far.
>
> I read somewhere that there is supposed to be 10 seconds of buffering
> built into the Chrysler/Sirius radios. So a disruption of less than 10
> seconds, like passing under an underpass on the interstate, would not
> disrupt the audio output. But my personal experience is that I lose
> the audio every time I go under an underpass, no matter how small it
> is or how fast I'm moving. I would say my radio has no buffering at
> all.
>
> For that reason, I would expect a canopy of trees to disrupt the
> signal. I bet the reception is better under those trees in the winter
> when there aren't any leaves.
>
> Dan

Buffering can't help a radio signal because the information is only
broadcast once, if it's lost it's lost. The reason buffering works for CDs
is because it's possible to go back and re-read the missed information.
The CD reader is much faster then it needs to be to play an audio CD,
think about the CDROM in your computer, it's probably 48X which means that
it reads at 48 time the speed that is needed to play audio. The CD player
in the car is just a CDROM reader so it can get way ahead, if the car hits
a bump and the head jumps it has plenty of time to reposition it before
the buffer runs dry. Obviously that can't work for radio unless they
broadcast the stream at least twice (simple error correction only works
for a few bits, it can't compensate for seconds worth of lost data).
Sirius would never choose to duplicate the data streams, if they had the
bandwidth for that they would just broadcast twice as many channels.