I'm running an hdmi cable to a 2nd tv (30 feet away). I have a 25 ft cable with an adapter to a 6 ft cable but the 2nd tv says low signal or no signal. Do I need an hdmi repeater or something like that? Plugging the hdmi in the 2nd tv also causes the main tv to go out.
HDMI repeater and/or amplifier boosts the HDMI signal and can be used for short runs. If you are looking for a reliable solution for long HDMI runs say over 100ft I would recommend using HDMI Extender products. You can check KVMSwitchTech as the offer HDMI booster and HDMI Extender solutions.