The particular receiver Theo was asking about uses a 6SQ7 dual-diode, triode
as a diode detector. I found it in the 1950 Radio Amateur's Handbook.

The schematic may be a bit misleading, though, since it shows a schematic of
the diode transformer that is the same as an if transformer - which is tuned
primary and tuned secondary - with the full winding on the secondary used
for the diode. I found this concise statement in the 1942 Editors and
Engineers Radio Handbook "Diodes load the tuned circuit to which they are
connected, however, and thus reduce selectivity slightly. Special i.f.
transformers are used for the purpose of providing a low-impedance input
circuit to the diode detector."

If I were winding the i.f. transformer, I would use a hi-q secondary and tap
down for the diode, so that selectivity is maintained, while properly
matching the diode input impedance. That may be how the transformer is
connected, although it does not show that on the schematic.

Colin K7FM