--- 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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