Lunar caves are subterranean wide and long tubes that could potentially host a human base. One of the key points in the future exploration of these caves is the communication network, which will allow to transmit the scientific data from the interior of the cave to the Moon surface. To establish a reliable link, an omnidirectional antenna, circularly polarized, has been developed in this work. The field of view (FoV) of the antenna is ±30º in elevation from the horizontal plane. The designed antenna has 0 dB gain in this FoV. The design is based on a pagoda antenna, and a ground plane has been added in order to reduce the interference with the metallic structure of a future explorer robot. Vibration simulations and a vacuum-thermal cycle (TVAC) test has been carried out. Finally, the antenna has been measured inside lava tubes in Lanzarote to ensure that this antenna will establish the communication link for a large set of the possible orientations of a mobile robot and in several possible scenarios in a Lunar exploration mission, including non-line-of-sight situations.