[RTTY] Sound Cards

[Joe Subich, W4TV]

> I'm wondering if there is any advantage or performance 
> improvement to be had with MMTTY and other RTTY programs by 
> using a 24-bit PCI card ? Tests done? Charts etc?

SDR operation is a very different paradigm than decoding 
the relatively narrow band audio spectrum for MMTTY, etc. 
The detected IF noise in the line output of most current 
transceivers is well above the noise floor of the run of 
the mill computer soundcard and maximum audio level with 
AGC is far less than the dynamic range of even a 16 bit 
card.  

Noise floor only becomes a problem with poorly designed 
laptops/motherboards - those that lack proper power supply 
filtering and decoupling - when driven by relatively low 
level outputs in some transceivers.  It's the "dirty power 
supply" issues that are overcome by USB soundcards or better 
filtered add-on cards.   

SDR operation in generally involves feeding broadband audio 
in I/Q to a soundcard without significant AGC.  Noise levels 
are much lower than the detector output of the conventional 
transceivers which makes both the noise floor and dynamic 
range of the soundcard significant when determining system  
performance.  
 
73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: rtty-bounces at contesting.com 
> [mailto:rtty-bounces at contesting.com] On Behalf Of rick darwicki
> Sent: Wednesday, January 20, 2010 11:23 AM
> To: Group RTTY
> Subject: [RTTY] Sound Cards
> 
> 
> Gents and ladies if you are out there,
> 
> I just ordered a little SoftRock SDR card and have been 
> reading about the performance with onboard vs PCI 24-bit 
> cards. The standard 16-bit 48 khz motherboard sound is really 
> a poor performer compared to a 24-bit PCI card.
> 
> I'm wondering if there is any advantage or performance 
> improvement to be had with MMTTY and other RTTY programs by 
> using a 24-bit PCI card ? Tests done? Charts etc?
> 
> Naturally the SDR needs stereo and the RTTY programs do not. 
> Maybe there is a program (or programmer wanting to write one) 
> out there that uses filtered audio to the R/L of a stereo 
> card for mark/space.
> 
> Rick, N6PE
> 
> ===============================================================
> 
> Remember, Some things are not worth doing well 
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