[BC] Asymmetrical modulation...

[Burt I. Weiner]

The negative and positive peak switch on a FM Modulation monitor 
refers to the direction of deviation from the carrier.  Negative 
peaks refers to the deviation in a negative or lower frequency 
direction and positive refers to the deviation in a positive or 
higher frequency direction.  This is one way to examine asymmetrical 
modulation.

The human voice, for example is typically not symmetrical.  If you 
were to look at (un-processed) voice on a scope you would see that 
some voice are heavier in the positive direction and others are 
heavier in the negative direction.  There are even a few voices that 
are somewhat symmetrical.

There are several things that could cause the symptoms you're seeing 
including improper FMO modulator bias.  I know there are some that 
will jump up and down when I suggest this, but if you can find a 
couple of old Symmetra Peaks of the same model, try putting them in 
the left and right audio lines right out of the console, ahead of any 
processing.

Burt

>
>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?
>
>The audio chain is:   Texar Audio Prisms to an Optimod 8100 (which was
>swapped out, still have issue) to a composite STL.. Using a QEI Exciter out
>of the STL receiver.
>
>Thanks
>
>Mark Gierhart