loss of signal

We lose our signal (cable) 3 or 4 times a day.  I remove the power supply to the router and it will reset.  I don't know or how to tell if I have a problem with the router or the incoming signal?  Is there a way I can determine which (if either) is the problem?  When I say we lose signal I mean the computer and TV's go off and say no signal and the computer says ( no internet).  They will be ok for a while after reset and then it has to be done again.  Can someone give me advice on what might be the problem?  Thank you in advance for your help.