[BC] Is overprocessing illegal?

[WFIFeng@aol.com]

In a message dated 12/25/2006 1:06:54 PM Eastern Standard Time, 
amstereoexp at yahoo.com writes:

> I do understand how putting unfiltered audio into an FM Stereo generator
>  will produce aliasing problems.  However, in my question I was talking
>  about a monaural FM station, at which no MPX generator is in use.  In that
>  case, it seems that as long as the 19 kHz pilot tone region is protected
>  (as the FCC rules require), then unfiltered audio above and below 19 kHz
>  would be of no consequence to the receiver.

Most radios are *not* that selective at rejecting signals up around 19Khz. 
They may, in fact, respond to anything between 18-20Khz. This will cause the 
stereo decoder to be false triggered on and off, with unpredictable (and usually 
nasty) results. I know, because I have experimented with *many* micro-powered 
FM transmitters over the years. The rejection of signals near 19Khz will be 
different on every receiver. If you really want to "push" the response of mono 
FM, hard-filter it at 17Khz. Most humans aren't going to hear much beyond that, 
anyway. There are some who are >30 years old whose hearing extends well above 
that, but they are the exceptions, not the rule.

Oterwise, just stick to convention and limit it at 15khz.

Willie...