Gmaptool splitted Bluecharts .imgs can become inappropriate, read:
[Only registered and activated users can see links. ]
You can use Homeport without an sd too, read:
[Only registered and activated users can see links. ]
New pads or phones have gps chip and compass embedded and their own Navigator applications.
For the intermittent connection problem I'm afraid you need an external antenna connected if you use it in a hartop boat