A large area RF source for negative ion-based injection systems has been developed and for the first time H - -current densities have been extracted which are comparable to those produced by conventional arc sources. This paper describes the design of the source and gives the results of H - -extraction experiments. A feature of this RF source is an increase of extracted ion current by up to a factor of four if noble gases are added to the hydrogen discharge. By this effect, a current density of 9 mA/cm 2 at 0.65 Pa has been achieved in volume production. With caesium seeding up to 20 mA/cm 2 could be extracted at 1 Pa source pressure with the addition of argon and a hot plasma grid. Recently, the RF source has been modified for long pulse operation by the installation of a Faraday screen.