Cell Signal Strength/Quality For Alarm Panels

What is an acceptable RSSI for a cellular alarm panel/cell communicator? I need to know when an external antenna (or amplifier) would be required.

Usually the panel or module will include a feature that gives you feedback on cell strength, ie: bars on the LCD or LED lights. There is not a good method of checking by sight or during pre-install surveys that I am aware of.

The signal strength depends on the type of network used by the panel. I know the basic impulse is to use a cellphone to see if the signal is strong in an area, but this method can be pretty inaccurate.

There are also some apps, some pretty good ones frankly that will do that. I am sure the manufacturer can give you the DB strength needed.

My experience with Honeywell and DSC indicated anything lower than -90dbi is considered bad, and warranting re-location or an antenna.

The honeywell GSM's require you to either have the GSM programmer, or log into the GSM programming through the system programming (*29 menu) and the DSC GSM's just give you two LED's (GS3060/3070 models) not sure if they've improved with newer models..

There is a RSSI mode for the unit and I have a couple of android apps that show signal strength, but I get conflicting results when switching modes, i.e. LTE, GSM, CDMA. So if I get a -80db average, I should be OK. Thanks for everyone's input.