The discrepancy in the GPS speed indication of the AS GPS HS antenna has been noted on several forums and with HB...

As of right now HB says it's caused by the difference in the way the individual GPS accessories calculate speed...

We will see what comes in the future as people start aquiring the iPilot Link and using them on the water...

For the present...you can only mentally adjust for the speed discrepancy until the HB future unfolds..

It probably wouldn't hurt to call HB or send them an email telling them your problem with the GPS speed discrepancy...

HB fixes stuff dependent on what the majority of their customers want...(the HB "Wishlist" does work...albeit slowly sometimes)...

Rickie