Need some help here on what to do about the Ground Plane for this ELT.

I want to mount their included 24" antenna inside the Fox behind the baggage compartment.

What do I do for a ground plane???

Artex instructions call for a 48" diameter ground plane for the antenna.

Called Artex Tech Support and he said he could not answer any questions regarding the ground plane for the antenna.

I'm removing my old 121.5 transponder. It did not have an external antenna, so there is no existing antenna mount.

Need the help of our electronics experts here on the forum.

Thanks

Regards
Rodney