I purchased the HHGPS from HB and connected my Garmin 276c to the 997 as the NMEA source (gps antenna).

$20 for the cable vs $150-$200 for an "antenna" makes sense to me and the results are about the same.

I believe you can accomplish this with about any hand held gps with NMEA out capabilities. FYI.

I installed the 997 in my Toyota to test it out. It works.

Thanks Humminbird Greg for the hints.

I now have a transportable 997. I plan to try it out on my Jon boat next week.