There is no requirement to ground an indoor or attic antenna.
Do you need to ground antenna in attic.
If you have no access it s hard for me to tell you to go to extremes to find a way.
Below is an image taken form the nec code book that shows how to properly ground a tv antenna.
Antennas mine are receive only for fm tv and public safety bands will be generally restricted to the attic.
Agreeing with adtech i don t see the nec requiring you to ground an indoor antenna system.
But if you have access to a ground connection that can serve the attic splitter it makes sense to use it.
If you look at the image below you ll want to use a 6 awg ground wire for all of your grounding runs and suitable ground clamps.
However the connection of your antenna coax to various ac operated equipment in this case your converter box or tv introduces the potential of electric shock.
Keep your grounding parts however.
Typically the house wiring and gutters represent a much lower impedance path to ground for lightning than the floating attic antenna.
If you find the attic install unsatisfactory and you move the antenna outside then you definitely do need it.
Some attics are dark unwelcoming places used only for extra storage and in those cases nearly any antenna will get the job done.
The nec requires that the antenna mast be grounded directly.