[BC] AM Digi Bandwidth (WAS:A bit disappointed.)

[WFIFeng@aol.com]

In a message dated 01/15/2006 11:11:06 PM Eastern Standard Time, 
Robertm at broadcast.net writes:

> Willie
>  
>  you could do this with no DIGITAL interference to the first adjacent and 
run 
>  anywhere from 5 to 10 kHz audio in analog. If you ran more than 5kHz you 
> would still interfere with the first adjacent on that side of the carrier 
just as 
> is the case today with pure NRSC analog stations.

I understand that part, naturally... but what I cannot quite grasp is how to 
add a digital subcarrier to an AM signal that would be non-interfering. Even 
using narrow PSK on the carrier at any kind of realistic data rate would still 
add noise & require some significant bandwidth.

Willie...