Fishfinder/GPS question?????

it has an external antenna mr. reel. i also have the dual frequency transducer wich is pretty neat.i can switch it from a wide cone for a better 'field of view' in shallow water to a narrow cone for better performance in deep water. wich is great for me. i like to hunt the shallows for reds and specks in the early morn, and then move out to deeper water and fish for grooper, lemons, cobia,etc... when it starts to get hot.