Hi,

This Bill Orr article may be what you are looking for -


http://www.thecompendium.net/radio/SW-3/SW3maginfo.pdf


Incidently, the large choke in the audio coupling circuit is
there to obtain as high an AC gain as possible at the expense of
a relatively low DC voltage drop. The fact that the grid leak and
coupling capacitor are all part of the same assembly suggests
that National used the same arrangement is several designs.


Cheers - Joe