Good afternoon @GERLINGSHOF1 and a warm welcome to our Community,
Good that you started a topic in regards to the problem with the signal strength and quality on your second TV. In some cases a coaxial signal amplifier is necessary as stated by our expert @Steefb. This may be the case when the distance between the connectionpoint (AOP) and the second TV is greater than 10 meters. Bear in mind that you should also use connectors, splitters and coaxialcables which meet the requirements of the cable quality mark (kabelkeurmerk). Connection materials with such a quality mark are extra well shielded against external signal influences (4G/5G radiation). In addition, the attenuation is generally less great per linear meter compared to a non-approved cable.
Before you intend to buy a signal amplifier you should first check the cables and connectors you're currently using by following the advice on these pages. It's possible that the problem can be resolved by replacing an old coaxialcable by a new one which meets the cable quality mark.