[JRTJH]

PARAPTOR is correct in stating that many of the newer digital TV's will blank the screen rather than show the "older" pixilated screen if the signal strength is low. Some have a "screen saver" that shows, "signal lost" or "no input" or some other floating notice that the TV is on, but has no acceptable input. Others simply go "blank" with a "black screen" when they lose signal strength. Why the 12VDC TV will function and the 120VAC TV will "drop off" is probably more a matter of tuner sensitivity than it is a malfunction. The blank screen would lead me to believe that when some 12 VDC powered device comes on, it drops the 12 VDC supply to to a level low enough that the amplifier in the TV booster cant amplify the output signal strength enough so that specific TV tuner can process the digital signal and blanks the screen as designed while the more sensitive tuner in the 12 VDC TV just keeps plugging along not even aware that the signal strength was decreased....

Now, why the signal is being reduced when either 120VAC appliances (HWH, coffee pot, etc) and 12VDC (furnace) is I think, the problem. My guess would be, similar to an automobile power supply, either corrosion on a battery terminal, a bad battery or a bad power converter output. I think I'd try unplugging the trailer from shore power, run an extension cord in the door to power the TV and run the trailer on the battery to see if it duplicates the problem. You may find that when the furnace comes on, the lights dim and everything drops out. That would indicate a battery problem. If, however everything works fine and the TV doesn't "blank the screen" then I'd suspect the power converter isn't providing enough power when the trailer is plugged into shore power.

NOTE: Add this to the mix.... Before any of the above unplugging and running extension cords is even considered, one should make certain that ALL of the coax connectors are tight and that the coax is fully seated in the connector before doing anything else. All of the above comments I've made deal more with the input signal strength than with anything else. If there is a loose connector anywhere in the system, from the top of the antenna all the way through to the final connector screwed into the back of the TV, the signal can as easily be "lost" in that loose connection as it can be compromised by a bad power supply, battery or anything else that may affect the antenna amplifier...... Check the connectors first !!!!!