I was reading that software version 6.3 is the highest for the 798c SI units (non HD) so in that case they will not be able to use the antennae due to not being able to install the appropriate software. The GPS puck that came with my 798 is a different model.
As for the newer HD units the AS GPS HS antennae webpage does not show anything below an 1159 unit as being compatible.
So at first glance it appears that this unit is not compatible. Someone from Humminbird or someone that has already tried to install it will have to provide an answer.