Your question is probably aimed at whether or not the German U-cruisers in 1918 established contact with German agents in the US. The transmission range of shipboard wireless equipment by 1918 was actually quite considerable (up to 3000 nm - depending on the atmospheric conditions) and that also went for those larger U-boats equipped as "communication boats" - and those were exclusively of the larger types. Their radios operated on a 400 metre wavelength - a very low frequency that requires very big aerials. Apart from the technical difficulty of transporting the required receiver (which would have been a very considerable vacuum-tube device) and the aerial, there is no corroborated evidence for U-boats in WW1 having contacted agents ashore.