According to:
COMMANDANT INSTRUCTION M16577.1:
Ch 3, Section C:
Frequency Tolerance: The carrier shall maintain a frequency accuracy within plus or minus 6ppm. (e.g., 2Hz for a 325KHz broadcast)
With stability like this, I think it would be useful to provide the current measurement from the recorded file with what it should be which could show the freq offset of the receiver.
Along with frequency measurement:
- What is the drift over time
- Do all stations show this drift or some or one?
- If more than one are drifting, are they consistent or have their own drift?
- Do stations in a region drift similarly?