Colin
The diode load resistor in most of the diode detector circuits I'm
familiar with have several hundred kilo ohms and I think 6SQ7 diode has
a few hundred ohms so the total reflected impedance to the last IF is
the pretty much the resistive load. And if my 68 yr old memory serves
me right most commonly used IF transformers had an input and output part
number and in some cases interstage but that may have been for TV IF. I
don't recall replacing many transformers because they failed
electrically but because the little ferrite core with a hex hole would
crack and could no longer be turned. Many times this was because of a
previous repair where a monkey not a tech, tried to tweak it and broke
the core.
I also worked on a one set that had the first IF transformer installed
backwards at the IF mfg factory, not the TV assembly plant. That took
some time to find considering the test eqpt at hand was limited to a
vtvm and an audio scope.
Time to stop rambling and ask if the ARRL article distinguished the IF
transformers with different part numbers?

--
Thanks & 73
Hank WD5JFR
"COLIN LAMB" wrote in message
m...
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