Valve Crystal Oscillator Grid Current

[Skywave]

First, why does the test rig that Al built only take 1mA of grid current although more or less the same circuit from my book take 40mA?

From my earlier post:
I do not know the cut of the crystal used in my experiment. If I had had a known X-cut type, I would have used that.

But that current is not being supplied by the grid! It isn't d.c. It is an r.f. current flowing through the crystal by virtue of the feedback capacitance from the anode of the valve. No d.c. current can flow through the crystal: as far as d.c. is concerned, the crystal looks like a low-value capacitor. And that is the salient point of the cct. that uses this bulb technique. With the triode crystal oscillator of yesteryear, (which this design is) it was common for that oscillator to supply at least 5-watts to the next stage. And that level of output of r.f. resulted in relatively large currents - r.f. currents - flowing through the crystal. So, try to draw too much r.f. power from the oscillator - the crystal current rises - and suddenly, poof! Exit one crystal.

Al.