47 CFR §80.1017

1. (a)An antenna must be provided for nonportable bridge-to-bridge radiotelephone installations which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in time of an emergency.
2. (b)In cases where portable bridge-to-bridge equipment is permanently associated with a vessel, the equipment must be provided with a connector for an external antenna of a type capable of meeting requirements of paragraph (a) of this section and § 80.71. The vessel must be equipped with an external antenna meeting requirements of paragraph (a) of this section and § 80.71, capable of use with the portable equipment during a normal listening watch.