RCA theremins - linear?

Just out of curiosity.

Can anyone comment on the linearity of the original RCA theremins.

Thanks

By all accounts, it is very good. The fact that the pitch range is limited to only four octaves may play a part, although there is reported to be a slight compression of the uppermost octave.

In 2004, Peter Pringle (coalport) created a linearity comparison diagram for his RCA, Ethervox, and Etherwave theremins.