The original message was weak signal and no channels showing in the guide.
Then the antenna short circuit message when I went to signal strength menu.
At that point no options are available.
Unplugging it I would just not be able to retune
Anyway connecting to a know good aerial enabled me to retune with strength 10/10
Then oddly going back without doing anything except having done the switching of power to aerial and reconnected gave 10/10 on the previous weak signal connection.