That worked, I cut off the black plastic piece and know I can plug in the bnc plug. Thank you very much.The black plastic part can be removed from the radio but it isn't easy. It is part of the antenna, not the radio. Uniden has supplied this antenna with several different models because the plastic BNC lock is cheaper than metal. Unfortunately once it is put on the radio it is very hard to remove. I'd suggest cutting it off - that way you won't be tempted to use this very poor quality antenna again. Most people who know about this antenna's problems never use it.
I should mention that the radio has a standard BNC jack on it. Be careful when cutting the plastic thing so you don't damage the BNC jack. Make a couple lengthwise cuts so the plastic can be spread enough to pull it off.