Due to their huge capitol costs, legacy alternator transmitters remained in use through about 1930.
2.
Only alternator transmitters like the Goldschmidt and Alexanderson could produce the high powers ( 50 to 200 kW ) necessary to communicate reliably at transoceanic distances.
3.
This matched, at a small fraction of the cost, the performance of the then-current RCA method for transatlantic radio, which used massive longwave Alexanderson alternator transmitters for producing signals that were sent and received using antennas with lengths measured in kilometers.