Protecting the antenna means providing lightning with an
alternative path to earth. Your building does that just fine.
But be better advised to earth using a lightning rod located
above the roof.

Safety ground system and earthing system share many
components. Different systems for different purposes with
some common parts. AC wall receptacle is not an earth
ground. An antenna is earthed so that lightning will not take
a more destructive path via the receiver. Ac receptacle
ground means lightning would spread out inside the building to
damage other electronics.

Connect things to the wall receptacle grounded screw to
protect human life. This is not same as earthing lightning.
To earth lightning, install Ben Franklin's well proven
solution above the roof. Earth incoming transients on utility
wires using either 'whole house' protector or a ground block -
all connected to a common earth ground that remains outside
the building.

Steve Rabinowitz wrote:
I guess the old way of attaching a wire to the screw that holds
the face plate of the electric outlet won't be any good then. I
could have swore my father years ago used that for grounding.