A sonde based antenna is used for communication within a wellbore. The sonde based antenna may include a toroidal antenna positioned about a conducting element. The sonde may be positionable within a gap sub. The sonde may be electrically connected to the first and second tubulars of the gap sub such that the tubulars are electrically coupled by the conducting element and are otherwise electrically insulated. The sonde may include a first and second structural member, the first and second structural members being electrically insulated except by the conducting element. The first and/or second structural element may extend through and/or around the toroidal antenna to, for example, add structural rigidity to the sonde.