Yes,the output power of a mobile signal repeater absolutely affects its coverage area .in general ,higher output power translates to a larger coverage area for the boosted signal . 

Here's how it works :

Strong signal ,wider reach :  a moible signal repeater receives a weak cellular signal ,amplifies it ,and then retransmits it . with a higher output power ,the repeater can broadcast the amplified signal further ,reaching more devices within a larger area . 

Balancing power and needs : it is important to find the right balance between output power and your speific needs .using excessively high output power can be counterproductive ,potentially causing interference with nearby cell towers or other devices . 

Additional factors affecting coverage : 

Freuquency :the cellular frequency being amplified by the repeater also plays a role .lower frequencies generally penetrate walls and travel further than higher frequencies . 

Antenna :the type and positioning of the antennas used with the repeater can significantly impact the direction and shape of the coverage area . 

Environment :obstacles like walls ,trees ,and even weather conditions can weaken the signal and limit the repeater's reach . 

Legality :

It is important to note that regulations regarding mobile signal repeater use vary by country .in some regions ,using them without proper authorization is illegal .always check the regulations in your area before using a mobile signal repeater .