My first try at a DIY (do-it-yourself) loading coil was done on an oatmeal box for the Ramsey AM25B, and it reached what seemed like resonance before I forgot what I was doing.
Two years later I built a triangular indoor coil-form from wooden dowels, corks and toothpicks, and upgraded an AMT3000 which today operates at full resonance driving a metal window frame.
But I remember the words of PhilB who said that we should be trying to build a better coil, one with very low resistance.
I think he might have said heavy gauge wire and an air core were two important ingredients.
I’m not sure which transmitter actually needs the better coil, but I’m going to build it.
You may be very old by then, but I intend filing a report.