WordNet (r) 3.0 (2006):

relay station
    n 1: an amplifier for restoring the strength of a transmitted
         signal [syn: booster, booster amplifier, booster
         station, relay link, relay station, relay
         transmitter]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "relay station":
   AM station, Comsat, FM station, Intelsat, RDF station, Syncom,
   Telstar, booster amplifiers, boosters, clear-channel station,
   communication satellite, direction-finder station,
   radio relay station, radio station, relay links, shortwave station,
   stratovision, studio, studio plant, ultrahigh-frequency station