What does it mean when a 'J' pops up on the V1 display? the only thing that I found that has a J in the manual was for instant pop...

 

I'm pretty sure it means it's error in reading... But I would slow down anyways if it's Ka bands

 

"J" is a "Junk" signal. The V1 will show this if it has determined that the signal it was picking up has come from a faulty source, such as another radar detector.

Some of the V1's without the newest version of the software have a problem with getting repeated false "J" signals.