Grumpy The Mule wrote:

But back to the SW3. I recall padder capacitors mounted on the
top of the RF stage coil former. I don't know the value of the
dual gang tuning capacitor but armed with that, Wheeler's formula
and these sites, you could calculate the effect of the grid circuit
to some extent.

http://www.io.com/~nielw/sw3coils.htm
http://www.antiqueradios.org/gazette/swevol.htm

Only the bandspread coils have the trimmer on top and thats basically to
set the rough frequency. The main tuning then becomes a bandspread
tuning. I've forgotten all this stuff - I'll have to look back at my
stuff...maybe the trimmer falls in series with the main tuning caps.

Anyway, thats just an example that came to mind. I've seen others doing
similar tricks for main tune/bandspread tune using the same cap but with
a different coil configuration.

-Bill