The Collaborative International Dictionary of English v.0.48:

Direct-coupled \Di*rect"-cou"pled\, a.
   Coupled without intermediate connections, as an engine and a
   dynamo.

   Direct-coupled antenna (Wireless Teleg.), an antenna
      connected electrically with one point of a closed
      oscillation circuit in syntony with it and earthed.
      [Webster 1913 Suppl.]