Tim Wescott wrote:
What are the three terminals of your oscillator? Your screen is
grounded, so I assume that the grid and cathode are both floating at RF
-- is this so?

The circuit is the "tuned plate Hartley" as it appeared in any
50's/60's/70's ARRL handbook.

The grid tuned circuit is at 1.8Mc, the bottom end of the inductor is
grounded, there's a tap nominally one third of the way up to the
cathode, and the top of the inductor is connected via a 100pF capacitor
to the grid, which has a 47K to ground.

The plate circuit in my current incarnation is tuned to the harmonic at
3.6Mc. The "untuned plate" version in the handbook has a RF choke
instead of a plate tuned circuit, and indeed I had this on the bench
for a little while.

Tim.