Roy Lewallen wrote:
"How did you conclude from this statement in Terman that the bandwidth
required by FM is twice that required by AM?"

Easy, I turn up the peak deviation intil twice the bandwidth is occupied
with FM as would be required for AM. It is arbitrary and depends on peak
deviation. If you make the deviation less than half the modulating
frequency, the bandwidth occupied will be about the same as required for
AM.

Best regards, Richard Harrison, KB5WZI