FM deviation meter

[AN920]

I am building a FM stereo transmitter from a kit and need to measure my modulation or also called deviation when on air. Where can I find a circuit to do this? The only thing I found was here http://www.edmdesign.com/mic.htm where they use a small radio. Any idea what the "additional electronics" would be and how they do it?

If I use the VU meters on a FM receiver, how can I calibrate it at 75kHz modulation?

[audioguru]

Hi AN920,
I think the "additional electronics" takes the audio signal before de-emphasis and peak detects it with a peak detector like in the datasheet for the LM3915. You can add your two stereo channels and it probably doesn't need to be before the de-emphasis because high audio frequencies usually aren't loud. Your VU meter is probably not a peak detector.

They say that rock stations frequently peak at 80kHz so measure a few stations and average their outputs.