[AMRadio] AM IARU Region 2 Bandplan

D. Chester k4kyv at charter.net
Mon Mar 8 18:47:45 EST 2010

> All that is need for communications grade AM is 300Hz to 3KHz audio. Just
> use a 6db/octave rolloff at 3KHz.
> There is not much 3KHz or higher energy in the human voice.And we are not
> supposed to be playing music.
> Bob Macklin

There is nothing in the rules that says we have to use "communications 
grade" audio (the space shuttle sound) on the ham bands.  Besides, there IS 
intelligibility information contained in frequencies above 3 kHz. The 
frequency range between 3 and 5 kHz contains most of the articulation, or 
sibilance sounds that make consonants clearly distinguishable from each 
other.  With space shuttle audio, some of this information is lost, and the 
human brain subconsciously attempts to fill in the missing pieces, so the 
casual listener may not be aware of what is missing but the message doesn't 
get through 100%.  That explains why SSB operators tend to use phonetics so 
often. This also causes listener fatigue after a short while.

Don k4kyv


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