> 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@contesting.com
> [mailto:rtty-bounces@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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