CB Newbie

I recently picked up a Radioshack Compact CB model # 2100164 to test the waters and see if I would like it enough to invest in a higher end model. Now when I purchased it I made no assumption that it would all that great but I paired it with a Radio Shack power supply and magnet mount antenna model # 21-801. I got it all setup and tested it inside my 2nd floor workshop as well as outside with the antenna mounted on the roof of my parents house today. Both times I was able to receive on two channels which appeared to be coming from Louisiana but I could be mistaken. Made an attempt to get a response on multiple channels including the "active" ones but didn't get anything. Only thing I could come up with was maybe it was a poor quality antenna as the reviews suggest so we went out to the two local Radioshack stores hoping to pick up a different antenna but there were no CB antennas at all so I picked up a TruckSpec 3ft antenna at a Flying J truck stop. After mounting it on the roof as a test the result was an increase in reception on the active channels and a poor broken up feed from someone that appeared to be much more local to me at the time but no response. Tonight when I got home I hooked up an old Sears RoadTalker 40 model # 934.38081700 I picked up from a thrift store a good while back and meant to play with but never got around to it. I hooked it up to try it out and see if my failures were due to a poor quality radio and tinkered a bit I found one active channel which the meter indicated it was a pretty good signal - I believe between 2 & 3 of the RF portion but all other channels were dead. I followed the manuals available to me with the exception of the Radiotalker and can't figure out what I am doing wrong. Any help would be greatly appreciated.

CB Newbie