Germany used a radio station at Sainte Assise, France for communicating with her submarines in 1942

American naval attaché at Paris, France reported in May 1942 that according to a reliable technical source Germany was able to communicate with her submarines operating off the American coast through a powerful radio station located at Sainte Assise near Melun, This could be easily recognized thanks to the erected tall towers. All messages originated from Lorient and were automatically rebroadcasted. 19,000 meters most frequently used. Destruction of this station woud affect a two week’s interruption of the communication and would force Germany to shifit over to the only other sufficiently powerful radio station namely, the one at Pontoise near Paris.

Source

National Archives USA. Record Group 38: Records of the Office of the Chief of Naval Operations. Series: Secret Naval Attaches Reports. Estimate of potential military strength (pt.). Summaries. Reports from London, Paris, Brussels, Rome and Berlin. Roll M975-001.