[HBR] Need advise: BFO coil not tapped

[Ian Wilson]

I have had good luck using Colpitts oscillators with untapped BFO coils,
at least at 455kHz.

You will want the series combination of the two capacitors to resonate
with the coil - say 150pF (assuming 100kHz).

You will want the cathode-grid capacitor to be smaller than the
cathode-ground
capacitor. Let's say 1:4 (this sets the capacitive tap, hence the gain): you
could
start with 750pF cathode-ground and 180pF cathode-grid (or 1000pF and 250pF,
and adjust the coil accordingly).

To avoid the need for an RFC in the cathode lead, you may need to put some
positive bias on the grid in order to use a large cathode resistor.

73, ian K3IMW