A direct receive ground connection to the NAV4 can help if the vessel suffers from the effects of high levels of electrical noise. To do this, a ground wire should be run from the antenna screen connection (2) of the NAV4 to a seawater grounding point nearby. A keel bolt or metal skin fitting could provide a suitable ground point. Care should be taken not to compromise the vessels galvanic protection systems. If this could be a problem a .1uf capacitor should be inserted in the ground cable. This will isolate the ground cable from any DC current flow.