[Elecraft] RE: AM bandwidth, the rest of the story :=)

[Joe Subich, W4TV]

> > I am sure the transmitters contain 
> > brickwall audio filters that allow flat response to 10 KHz while 
> > still meeting the standard at 10.5 KHz. 
> 
> It's actually 10.2 kHz, not 10.5.  I don't think I'm going too far out
> on a limb to state that it's absolutely impossible to build an analog
> filter that is flat to 10 kHz but down 25 dB at 10.2 kHz.  It might be
> possible to do that with a digital filter, but remember DSP 
> wasn't even thought of when those regulations were written.

There s no doubt the modern transmitters don't use analog filters. 
They're all using digital filtering of the audio and digital modulation 
methods.  However, even 30 years ago before many of the digital methods   
transmitters were making 8 KHz or more of audio bandwidth while still 
meeting the limits at 10.2 KHz. 

73, 

   ... Joe, W4TV