Here are some things to pay attention to when installing a mobile signal repeater : 

Before installation : 

Legality :make sure that using a mobile signal repeater is legal in your area . some countries and regions have restrictions on the use of those devices . 

Compatibility : check that the repeater is compatible with your cellular carrier and the frequencies they use . 

Signal strngth :make sure that there is a weak but usable signal outside where you plan to install the outdoor antenna .if there is no signal at all , a repeater will not work . 

Placement : the outdoor antenna should be installed in a location where it can receive the strongest possible signal from the cell tower . it should also be at least 20 feet away from the indoor antenna to avoid feedback . 

During installation : 

Safety:be careful when working with ladders or on roofs .make sure that all connections are secure and weatherproof . 

Cable length : use the shortest possible length of cable to connect the antennas to the repeater .long cables can reduce the signal strength . 

Alignment :the antennas should be aligned aorrectly .the outdoor antenna should be pointed towards the cell tower ,and the indoor antenna should be positioned to cover the area where you need improved signal . 

After installation : 

Teating： test the repeater to make sure that it is working properly . you should see an improvement in your signal stength . 

Monitoring : keep an eye on the repeater and make sure that it is not causing any interference with other devices . 

Here are some additional tips : 

If you are not comfortable installing the repeater yourself ,you can hire a professional to do it for you . 

There are many different types of mobile signal repeaters available on the market ,do some research to choose one that is right for your needs . 

Be aware that using a mobile signal repeater can increase your battery drain .