[BC] Negative Peaks

[Phil Alexander]

The likely suspects are mod monitor out of calibration or asymmetric
amplification at any point including the modulator in the exciter.

First - check the calibration of the mod monitor if you have or can
borrow a spectrum analyzer. Look up Bessel zero method if you
are not familiar with it. This is where the modulating frequency
and modulating level cause all power to appear in the sidebands.
IOW zero carrier. If you can't do this, then sendind it back to the
factory for calibration might be the best option.

If that is OK, plug an audio generator directly into the exciter and bring
up the output slowly through the 90 - 100% range and observe.

If modulation is symmetrical, step back through each stage of the
audio chain until you find the source of unbalanced audio.

Phil Alexander, CSRE, AMD
 

-----Original Message-----
>From: "Mark Gierhart" <markg at watchtv.net>
>
>Folks,
>
>I have an FM that has Negative Peaks about 6 percent higher than my
>positive peaks.. I know on AM this can be a reversal of the analog audio..
>What would cause this on FM?