Argamis

Having both a "relay" antenna PLUS a "direct" antenna on the same ship has a combined benefit on signal strength transmission if the science transmitted comes from the satelite itself [but unless it was generated with its own instruments; then this requires a physical "docking" or "manual" (EVA kerbal) conection for storing the data inside the satelite]. There is also a +40% "extra magical bonus" science [as long as the "experiment" can not be sent at 100% of its value [like crew reports]; if it bounces on at least another relay antenna (not in the same ship were the data starts its transmission); this bonus gets diminished if the signal strenght [using only the relays antennas on both ships for the calculations] is not 100% through the whole chain back to Kerbin. -> This is based on real life "radio experiments" that uses the same protocol for encriptation and error correction to study the space transversed by the radio signals and its carrier beam (since the "real" original information is later reconstructed perfectly, it is posible to use the "errors" themselves as if they were "shadows" caused by the interplanetary medium over the "light" of the transmission).