[AMRadio] AM Transmitter "quality"


Grant Youngman nq5t at tx.rr.com
Tue Sep 15 14:31:40 EDT 2009


On Sep 15, 2009, at 1:11 PM, Joe Hankins wrote:

> I
> operation was effective radiotelephone service. Human speech falls  
> into
> the range between 300 and 3000 Hz. There are sounds outside this  
> range,
> but they do not contribute to intelligibility.

That's actually a complete myth.  There are frequency components both  
above and below this range which, if present, contribute in a major  
way to speech intelligibility.  The fundamental frequency in  vowels  
is closer to 100 Hz, and frequencies well above 3 Khz (actually above  
4Khz) are needed to reliably distinguish an "f" from an "s".  There  
are also significant intelligibility cues in the 20-80Hz range for  
some consonants.

300-3000 hz was convenient for the phone company and was proselytized  
by Collins (which we all know is never incorrect in design philosophy)  
as the gospel truth.  But it  contributed mostly to Uncle Bob and  
Granny being so hard to understand and sounding so lousy on the  
telephone.  And contributes still to "pinched" sounding radios.  Your  
modern telephone (fortunately) exceeds this old accepted range in  
bandwidth.

Grant/NQ5T


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