We have the King Jack in ours and it's a really good antenna. I'd suspect that something is not connected correctly or came unconnected.
The number of Jayco owners who've posted similar woes only to find out that Jayco didn't connect things properly - well, they're quite a few.
In answer to your question - if you plan on using the same King Jack wiring from the TV to the new antenna, I guess that'll answer your question.
But before I bailed on the King, I'd just grab some RG-6 and wire direct from the TV to the new antenna. If that works, then I'd use the King Jack wiring to the new antenna.
If that fails, then you know it's the wiring and not the King Jack.
2016 Greyhawk 31FK