reply to Max Signal
Re: Debugging slow speed It's a metal roof. Magnet sticks to it. It is not tin, aluminum or stainless steel.
check all your connections , something not right , you should be around -80 or better , with amplifier and antenna , starting -109
Also is roof flat or slanted ? Antenna must be perpendicular to ground to work best . If slanted roof , that could also be having a negative impact .