Direction Finder Antenna in the market

Hi all,

Anyone has any idea why Direction Finder Antenna in the market only up to 3GHz? However, the monitoring receiver can go up to 20 GHz

cuz up to ~3 GHz its very easy to use yagi antennas and coax
from ~ 10 GHz and up it would be more common to use waveguide and horn antennas or something similar
and that is quite a bit more specialised

Dave