[WriteLog] USB Sound and Rig Interfaces

[Joe Subich, W4TV]

Howard White writes: 
 
> BTW... External USB Sound Card Devices such as Rig Expert 
> work substantially better (10db or so) than internal sound 
> card on digital signals.. 

This is demonstrably false.  The claimed "advantage" comes from 
flawed tests which fail to properly set the input level to each 
sound device to take maximum advantage of its dynamic range. 

Except for the very worst sound cards or exceptionally noisy 
systems, internal sound cards have at least 60 dB of usable 
dynamic range (the better 16 bit cards have 80 dB of dynamic 
range and 24 bit cards with high level inputs can have dynamic 
ranges that approach 100 dB).  If the audio from the transceiver 
is such that the receiver noise floor (no antenna) is six to ten 
dB above the noise floor of the sound card, the software DSP 
(RTTYrite, MMTTY, etc.) will be able to operate at its full 
capacity.  Receiver AGC, etc. will limit the receiver output 
to a level well below the input capacity of the soundcard.  
Most receivers will not vary more than 30 to 40 dB from quiet 
band to S9 +40 dB receive signals.  

Soundcard performance is not a matter of internal vs. external. 
It is a matter of careful attention to setting the proper level 
to allow the soundcard to function properly. 

73, 

   ... Joe Subich, W4TV 
       microHAM America 
       http://www.microHAM-USA.com 
       http://groups.yahoo.com/group/microHAM 
       support at microham.com