[HBR] Triode mixers

[Ian Wilson]

Working from the back to the front of a dual-conversion RX loosely modelled
on
the 75S-3C, I have reached the first mixer. This is the triode part of a
6EA8 in
the Collins RX. The xtal osc output is injected into the cathode.

I am attempting to use half a 6DJ8 for this, but it isn't working well. I
suspect
that I need to have a cathode circuit that is low impedance except at the
injection frequency. Otherwise this looks rather like an oscillator. The
Collins
circuit essentially takes the xtal osc output from a 100 ohm load in the
plate
of the pentode half of a 6EA8. Across this 100 ohm load is the (untuned)
primary of a transformer, the (tuned) secondary of which provides the
cathode
injection for the mixer. I have no information about the transformer;
however,
the AC injection voltage is shown as 1v on the schematic.

Would welcome general info on cathode-driver triode mixers and/or pointers
to schematics on BAMA of receivers that use this, hopefully without
components
that are difficult to reverse engineer.

73, ian K3IMW