[BC] Analog AM bandwidth: tail wagging the dog?

[R A Meuser]

Bob:


I have had great success in the analog world with a 5 kHz bessel filter 
with extra poles added so that the response is severely attenuated at 7 
or 7.5 kHz and upward. It seems no matter what response is chosen there 
are always issues with having audio response right up to the sharp cut 
off of the final filter. Maybe you and/or Frank might consider an 
adjustable prior to the multi band section in some future processor. 
The parametric EQ in the 9400 can accomplish some of this but a 
dedicated LP filter would be much better.




Robert Orban wrote:
> At 06:19 PM 10/3/2007, you wrote:
> 
>> Bob Orban wrote:
>> > I believe that a significant reason that the final preferred
>> > bandwidth was 7 kHz was that broadcasting wider bandwidths puts more
>> > stress on the audio processor. If the processor clips material
>> > between 7 and 10 kHz (to which a vast majority of AM radios are
>> > essentially deaf), the resulting clipping distortion products *will*
>> > end up in the 0 to 3 kHz frequency and *will* be heard on typical
>> > radios.
>>
>> That's all the more reason why audio above 6 kHz or so should be given 
>> its
>> own band in the processor's multiband compressor/limiter structure, like
>> your 9100 did, so that most of the HF gain control can be achieved before
>> the audio hits the clipper(s).
> 
> 
> This comment misses the point. If the transmission includes energy 
> between 7 and 10 kHz, it takes up extra "room" in the modulation 
> envelope. Getting a 0 - 10 kHz bandwidth transmission to sound as loud 
> as a 0 - 7 kHz transmission on an average radio requires the audio to be 
> clipped and limited harder, regardless of the details of how it is done 
> in the audio processor.
> 
> bob Orban