Hi
The best way to ensure that your signals are good is to use a moniter tv rather than a signal strength meter.
Many aerial contractors just sit the areial up on a roof and point it in the general direction.
The best way is to attach a cable to the arial and walk the site and choose the best signal IE no ghosting colour fade and grain . A signal strength meter can be of use but it will only show you signal gain and after all it is the quolity of the picture you want. The signal strength will very any way with weather and other conditions.
Barrybear