I may be duplicating the web and can not vet the answer but there is some talk about deleting all channels on Antenna. Try researching that workaround.
So for the last few weeks my UN46F6350 has started to switch (?) to the TV/Antenna source when it is off for more than a few minutes. Before this it was always on the HDMI source, which is all we ever use as the Comcast box we use is HDMI. This is a mere 5 second long inconvenience as it can be solved by hitting the source button and switching to HDMI.
I checked all the settings and made sure the firmware was up to date. I then used the chat feature to speak with "Preston". This is the short chat that followed:
Preston: Hi, thank you for reaching out to Samsung technical support. How may I assist you?
Preston: Hello, how may I assist you today?
Visitor: Hello, I have a UN46F6350 TV. In the past few weeks when the TV has been of for more than a few hours and we turn it back on, the source is set to TV/Antenna. The only source we use is the HDMI. Not the biggest deal as all we have to do is hit the source button, but still something I'd like to fix
Preston: Thank you for the information.
Preston: I understand that the TV source is changed to TV when the TV is powered OFF. Is that correct?
Preston: Thank you for confirming.
Preston: I have checked the details.
Preston: The TV will default the source to TV/Antenna when you power OFF the TV and turn it ON. It is the specification of the TV.
Visitor: So the TV is designed to start up with static every time if someone is not using an Antenna?
Preston: Yes, the source will be set to TV when you power OFF and power ON the TV.
Visitor: Good to know. Thank You.
I have trouble believing that a TV they constantly point out is Smart would be designed to display static on start up for every user who uses HDMI as their primary source. Call me crazy, but I think that would be odd.