--- Kevin der Kinderen <[EMAIL PROTECTED]> wrote:
> I'm geeking here, so don't say I'm wasting my time.
> I already know that. ;-)
>
> How much does the quality of the soundcard affect
> the quality of the
> transmitted (or even received) signal?
Sampling clock frequency may be critical with cheap
cards under Windows.
> Are the
> current modes (PSK,
> MFSK, RTTY) not so critical that the differences
> between soundcards
> are "below the noise level?"
Depends on the quality of the sound blaster chipset...
> On PSK I have been playing with various settings of
> DIG GAIN (FT-
> 897D) and audio out from the sound card to find the
> best IMD as read
> on my KK7UQ meter. The best I can get is -30 dB IMD
> by having most of
> the controls near the mid-range.
That is usually the best that linear power amplifiers
perform "in the real world" in ham rigs. Some pro
stuff might fare a bit better, down to -40 dB IMD, but
those radios are rare among hams and expensive.
> If I max out the audio from the
> computer and back down the DIG GAIN to compensate,
> my best IMD drops to maybe -25 dB. This leads me to
> believe the soundboard quality can make a
difference.
Yes, it all adds up...
> I'm considering an M-Audio soundcard to play around
> with and see what
> differences that might make. The model I'm looking
> at is 2496
> (getting a great price used).
>
> Is there a method of measuring IMD at the soundcard
> before it even
> reaches the radio? Does that spec even apply at that
> level?
You could, but the worst offenders are usually the
higher level stages, the power amplifiers.
> The specs that seem to make a difference are:
> 24-bit/96KHz
> Freq Response: 22Hz-22KHz, -0.4, +/-0.4dB
> Dynamic Range: 104dB (D/A) 100.4dB (A/D)
> THD: <0.002%
>
> The specs I found online for my current Ensoniq PCI
> (Soundblaster)
> card are:
> 16-bit/48KHz
> Freq Response: 50Hz-15KHz +/-0.1dB
> Dynamic Range: 81.3dB to 79.5dB
> THD: .006% to .018%
>
> Again, just geeking. But definitely would be
> interested in hearing
> from others that might have contemplated this issue.
>
> 73 de KJ4QF
> Kevin
Good luck. Will be watching for comments on the
list...
Jose, CO2JA
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