Tuned Input for the Grounded Grid GS-35B triode.
The tuned input circuit is necessary to keep the IMD down in this amp and all grounded-grid amps. Many of the amps heard on the band could benefit from a tuned input and there is no reason not to build this amp with one.
Other than the band switching problem, actual construction of the tuned input circuit is pretty straight forward and there are lots of links to help us decide how to go about this. I'm not claiming any original work here other than trying to point out the information.Links