RE: [amsat-bb] FM vs SSB

[Jean-Louis.RAULT@xxxxxxxxxxxxxxxxxx]

John

I wonder if the articulation index isn't influenced by some fuzzy parameters
such as:

- language itself
- regional accent for a given language
- number of teeth in the mouth
- ear audio passband
- wakening status of the listener
- etc 

:o)

73 de Jean-Louis F6AGR

> -----Message d'origine-----
> De : John Stephensen [mailto:kd6ozh@gte.net]
> Envoyé : vendredi 25 juillet 2003 09:02
> À : amsat-bb@AMSAT.Org
> Objet : [amsat-bb] FM vs SSB
> 
> 
> Here is some interesting data for transponder designers. The 
> table compares
> the modulation types by the received signal level required for an
> articulation index of 30%.
> 
> Unprocessed     Processed       RF
> PEP     Avg.    PEP    Avg.    PEP     BW     Mod.
> 39      53      35      42       3      SSB
> 39      53      35      42       6      DSB
> 45      45      41      41       6      FM
> 46      46      42      42      12     FM
> 54      59      43      48       6      AM
> Source: Sabin & Schoenike, "HF Radio Systems and Circuits"
> 
> The articulation index is the percentage of spoken words 
> received correctly.
> The audio bandwidth in all cases is 300-3000 Hz. Processed speech is
> preemphasized by +6dB/octave above 500 Hz to prevent loss of 
> the weaker
> high-frequency components in the human voice and then clipped to a 7dB
> peak-to-average power ratio. The power levels are in dB above 
> the receiver
> IF noise level in one Hz so that they are proportional the 
> power output at
> the transmitter regardless of receiver bandwidth..
> 
> Note that narrowband FM requires the lowest peak power level. 
> SSB requires
> the lowest average power level.
> 
> 73,
> 
> John
> KD6OZH
> 
> 
> 
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