Thank you all for comments and suggestions.
Kevin and Chuck were right: It was an old PL-259 center pin casing from another antenna that stayed in the radio. Your comments pointed me in the right direction, and once I was able to visualize what had happened, it was easy to figure out what to do.
So I am back on the air and glad to be working again with my FT-8800, which is a great radio.
Thanks again.
Regards,
VA7BLR
