FM rooftop antenna grounding problem

You really need a directional outdoor antenna. The FM2G doesn`t cut it. Your poor reception has ZERO to do with grounding.

Michael, are you in an urban area (less than 75 miles) and have line-of-sight to the broadcasting towers, or are you out in the middle of the great plains??

That was a rhetorical question ;-) if you had adequate gain (signal strength) in the basement, you should have more than enough with the whip (omnidirectional) antenna on the roof as long as it's at least 6 feet away (horizontally) from any grounded obstructions (like air conditioner units, other antenna towers, fire ladders, etc.)

Whatever the cause, the signal from the antenna ain't gettin' to your tuner. Could be a short in the coax or in the connectors somewhere. Could be the "device" is faulty, or you have it installed backwards. Try it first without the "device", using a simple double-ended female coupler to connect the inside and outside coax. If the problem persists, one or both lengths of coax is/are shorted. Also (and this is important, believe it or not) make sure all your coax is of the same kind (same spec number printed on the outside). Mixing coax types in the same run is a no no.

My guess is the grounding device is bad or installed backward.