[Today’s run: 3.5 miles]
One of my recent auction purchase is an automatic FM modulation meter.
FM stands for Frequency Modulation. Which means that the frequency of the signal changes from some nominal value in order to carry the information to be transferred. In layman’s terms, the frequency of the signal wobbles away from the central frequency, with a “louder” signal being a bigger wobble. The “speed” of change of the wobbles would be the musical note, and the spread of the wobbles would be the loudness. The actual strength of the FM carrier itself stays the same all of the time. It is these frequency excursions that contain the information.
(I think I have that right… I always find modulation to be a bit of a mind-bender.)
As you can imagine, most FM broadcasters would love their signal to be louder than everyone else’s and have a big fat wobble. But then they would be bumping into other stations on either side and it would be messy.
For our little FM station we want to have as much modulation as we are legally allowed to have, but not any more than that.
I have done some measurements with the spectrum analyzer to make sure we were in the neighborhood of good. Now I have an actual modulation meter. A quick check seemed to indicate we were doing pretty well. I need to a) find the manual for the thing online and read it, then b) do a true measurement and tweak our signal as necessary.