"econof" wrote in message news:dElpb.70518$ao4.195390@attbi_s51...
I recently installed a cobra 29 in my Ford Explorer. I understand the
previous owner had the radio "tuned".

DUH. "Tuned" means some CB butcher clipped the harmonic filters out of the radio.

If I key the mike while my factory car
stereo is on, I can hear it through the speakers.

What did you expect?