Managed to fix the reception issue with the portable antenna powerer. When I use the TV with that feature built in, the HD channels work fine.
When I try to click on one in the JRiver panel, it'll freeze whatever is on the screen and won't show the channel. JRiver doesn't lock up though, I can change to any other channel and it'll work.
I've tried literally every other DVB program I can find on google and not a single other will even acknowledge the HD channels exist, so could well be an issue that isn't related to JRiver. Seems to work ok apart from the HD channels.
I have a TBS dual tuner 6280, and haswell build.