Believe it or not.....when all of the satellite transmissions were C Band analog, it was possible to listen in on telephone conversations. You could only hear one side of the conversation, and you could not understand the conversation very well, if at all. I played with it for a while, using my shortwave receiver, but found it boring as compared to watching all of the unscrambled cable TV and wild feed transmissions that were available.
The old C Band receivers all had a "baseband out" connection on the back panel. The "baseband" signal could be processed, with a regular shortwave radio receiver, to actually listen to phone conversations that were being transmitted via C Band satellite. Some of the transmissions used the upper and lower sidebands, just like shortwave and ham radio bands were using.
Most satellites carried television, data, and telephone streams at the same time on different transponders. Later, some satellites were dedicated to telephone streams only. None of the streams were scrambled and were easy to decode. For each television transponder to carry one stream, a transponder dedicated to data or telephone could carry thousands of streams. Many of the televisions streams carried sideband radio transmissions, just as it's being done on Ku now, if your receiver had tuneable audio, you could listen thru your TV. However, most receivers would only tune 6.8 or 7.2 Mhz. audio channels and wouldn't work well. I remember listening to thousands of radio network and independent stations just on the television transponders.
This was a touchy subject concerning Federal Communications Commission's enforcement of the laws at the time. It wasn't illegal to intercept the transmissions, but it was illegal to use the information from the transmissions for anything other than just listening. Laws were later changed, added, and adapted to make even the interception illegal.
Things like the telephone and wild feeds have made this hobby the most interesting one that I could have even imagined for more than twenty years.
Harold