LCD TV 12 volt power cord

It's your converter. It's putting out "noise".
A less likely scenario is you have a florescent or LED light fixture that's creating the AC component.

Unplug your trailer from shore power and see if that helps...

My older converter did the same thing here if it was turned-on while I was hooked up directly to the battery...

Like said above alot of things are still connected to your 12VDC Battery terminals that can cause interference like this...

You might want to totally disconnect the battery and see if the TV set works fine just connected to the battery without anything else connected.

Of course doing this you may lose your 12V DC signal going to your BATWING built-in Boost Amplifier so your TV signals may go away as well...

Roy Ken

12 volt fluorescent lights?
a cheap inverter
fans.
can all cause interference

No, I am using straight battery power. When I am hooked up I can use the 120 volt cord that came with it.

mrbreeze az wrote:
I picked up an Insignia 28" LCD TV that has 12 volt input. The TV works well using the residential 120 volt cord that came with it. I bought a 12 volt cord and it powers the TV but has wavy lines going up the screen constantly. Has anyone experienced this? Maybe I need a different power cord? Thanks in advance.

If you are using battery power, and not plugged into shore power, there should be no interference. If you are using power while the converter is in operation, that may be the problem.