Today's Mystery Guest (RCA CTC-4)

[old_coot88]

Is that a low capacitance scope probe? If not, it may be pulling the tank freq down too much. To minimize loading, you could add a small cap in series with the probe. Just a 'gimmick' consisting of a few inches of wire twisted together should do it.

If you need to raise the freq, try a lower value tank cap. Maybe 100 pf to start, and see which direction you have to go from there.