It has nothing to do with hard drive
Whatever picture quality problems you are experiencing are not due to the hard drive. The signal is encoded/compressed/modulated etc. by the satellite service provider at their transmission/uplink facilities. It goes up to the satellite and then back down to you. Your receiver gets that signal and converts it to a data stream. The electronics in the receiver then decode the data stream and pass the picture in a signal format that can be displayed by your TV. To the best of my knowledge, the receiver does not have recode and recompress the signal (doesn't make sense) before storing it on the hard drive. Therefore, all the hard drive does is store a copy of the digital bitstream that your receiver receives from the satellite.
The primary factors that CAN influence the picture quality are:
1) Quality of source. If SC is getting poor quality video (no matter how it's provided to them), there's not much they can do with. The rule is garbage in = garbage out.
2) What SC is doing to the picture before they transmit it. If they are overcompressing, using poor modulation, or a number of other technical things that I won't pretend to understand the details of, then that could adversely affect the picture quality. From what I've read on the forums, SC is one of the better TV programming providers with regard to picture quality. They don't seem to have bandwidth constraints like DirecTV or some of the cable providers and don't have to overcompress.
3) What's going on between your sat receiver and your TV. Part A of this lies in the electronics of your SC receiver. If the electronics in your satellite receiver are of poor quality, they may do a poor job of decoding the data stream and providing a good signal for your TV. I don't think this is the culprit.
Part B is the signal that goes out from the back of the receiver to the TV. There are a number of ways to get the picture to your TV from the satellite box. They are (from worst to best): RF modulation (transmitting the signal like a regular TV channel over a coax cable to your TV, usually on channel 3 or 4), composite video, S-video, component (used for analog HD), and DVI or HDMI (used for digital HD).
If your TV is a modern set, then using DVI or HDMI will send a digital signal to the TV that it decodes and displays. This gives the best picture for HD and the best for SD in most circumstances. Component is your next best choice for both HD and SD, again in most circumstances. A TV with superior electronics will usually do a decent job of cleaning up a muddy SD picture, but it will be limited in how much it can do by what it's getting from the receiver.
In other circumstances, the SD outputs (also know as analog outputs) on your sat receiver (coax, composite, S-video) may do a better job of feeding your TV a good signal, especially if you TV is an analog model (i.e., not HD or ED). You should try those outputs to see if the picure quality for SD channels improves. Again, if inferior components are being used to produce the output, you will get a poor picture. Also, keep in mind that your SC receiver is not going put out exactly the same signal that your BEV receiver does. There will be differences in the levels of hue, saturation, etc. The differences may be vast enough to make a visible difference in picture quality and require you to make adjustments to your TV.
The final element in the chain is your TV and this ties in with the last point I just made. Try making adjustments color, contrast, and other settings to improve picture quality. You may notice a big improvement after you fiddle around a little bit.
Finally, don't forget the cables that link your receiver to your TV. If the cables are poor quality or have a flaw in them such as exposed wiring, then this can cause problems too.
I think your problems will be solved by adjusting your TV or switching to analog output (or changing which analog output you are using).
In the end, there may not be too much that you can do about it. It's common knowledge that SD video looks awful when it converted to HD. The garbage in = garbage out rule applies to every step of the chain.
Hopes this helps.
