Always "searching for signal"

We have 2 of these recievers in this house. One works great, however the main receiver is forever "searching for signal" just from mainly changing the channel or every morn when I turn the damn thing on.The other one works just fine, great signal , everything....so why is the main on ALWAYS and FOREVER messing up? you would think that having to pay so much a month to watch T.V. that you could at least get a signal to last more then an hour......Any body else got this problem?