In case anyone else can benefit, I partially answered my own question.
If the tuner doesn't detect an OTA digital signal it will automatically switch over to analog search. It then stays in analog mode. I tried unhooking my antenna and then plugging it back in. The only way I could get the digital channel to show up was by switching the channel. Makes it pretty useless for antenna adjusting when there is no signal to begin with unless there is some way to prevent the TV from using analog at all.
Still no idea if there is a built in FM trap.
I own the LN46C670 LCD. Does the over the air tuner have a built in FM trap to screen out FM interference for VHF channels? If not I was going to buy one and try it for a difficult to receive station.
Also, if I have it on a channel that can't get a signal the TV switches to "Air" analog search and shows a snowy picture. If a digital signal suddenly comes in, will the tuner automatically pick it up even though its a digital signal and the TV is on analog search? Thanks.