I need to extend an HDMI signal to about 90 feet to reach my main TV (an older Hitachi Plasma). I purchased an HDMI over Coax extender and it works great with my bedroom TV (a newer LCD) but I get no picture and no sound on my older (2006) Hitachi Plasma. I tested it with yet a 3rd new LCD and it worked great... so I have narrowed it down to my plasma. I tried connecting my source directly to the plasma and it works fine... but when I throw the Coax extender into the mix... nothing. Does the old HDMI (2006 and earlier) have disadvantages? Could it be that my plasma is 720P?