Do signal boosters work?

[SLVR2003]

Do signal boosters work at all?
If so how well?
I bought one that has these specs.: For AM/FM Provides 20 dB gain. Any 12V application Easy dash installation
I also bought a different one that is said to boost my TV reception.

Bottom line I need to know are they worth installing?

[Atomic]

Basically the booster takes the signal and amplifies it(makes it louder, not better), but if you're getting any kind of static it'll amplify that too. Better reception really depends on the quality of the tuner in your headunit, partly on the length of the antenna(i.e. get rid of the aftermarket shortie antenna if you have one) and location of the antenna for the TV tuner. I'd say give it a shot, they're really not that hard to install and if you don't like it, pack it up and take it back.

[SLVR2003]

The TV one is like a film with copper inside it. It mounts to the rear window so I don't want to stick it on if it's not going to improve the signal quite a bit.