Yes they do that Nigel:
When I was in the Test and Measurement business for Tektronix, we used
to laugh at the internal test instrumentation cards for PC's..that
in-the-box environment is pretty noisey.
I have used the on-board sound systems in laptops and on PC boards based
on the AC77 s/w model..they work but indeed don't do a very good job.
Again, my experience with the SB 16 card has been good tho..even with
WSPR which is a truly weak signal mode with decodes from around the
globe on milliwatts not uncommon. I also have used one of the Creative
cards that Simon mentioned. It is at the upper end of the "consumer" or
"gamer" realm. The semi-pro audio stuff like M/Audio Delta44's are MUCH
better but it is a large price to pay for very small practical
improvements in everyday operation. (JMO)
The Creative Audigy series just places the mic preamps and I/o
external..I suspect( not 100%) that the A/D are still on the internal
part of the split system..so while it is more convenient, it isn't much
quieter than the internal, non-split, version. Of course the
USB-connected devices you mention are probably the best, noise wise..or
at least they COULD be..because anytime you put a high speed digital com
capability inside an audio box, the potential exists for noise problems.
There are some very good comparison charts that have been made up by/for
the SDR community that rate the noise floor and dynamic range of a
variety of the better cards available. Last time I looked the Delta44
was pretty much the best widely available. Check the Softrock yahoo
group files and links..pretty sure its there.
Cheers,
Curt
Nigel Gunn G8IFF/W8IFF wrote:
Hi Curt.
The biggest difference is in the location rather than design of the card.
That inside a desktop or laptop PC tends to pick up significantly more
noise fron the other circuitry than an external USB card.
Ensure that you turn off the Windows burps and farts and other sound
effects or they will be transmitted along with your wanted signal.
This from the Ham Radio Deluxe Interfaces Manual by Simon Brown and
Peter Halpin.
(
http://www.ham-radio-deluxe.com/Portals/1/Documentation/Interfaces.pdf )
"And one last tip: the onboard soundcards supplied with many computers
are very basic indeed. Many people report seeing "ghost" signals on
their waterfalls: these are very often caused by below-par soundcards.
If you can install a good one - I use a Creative Audigy 2 - you will
be pleasantly surprised at how 'clean' the waterfall looks. An added
bonus is that you will be able to decode weaker signals too! Adding a
second soundcard to any system can be recommended: but please make
sure it's a good one."
On 17-Sep-10 13:51, Curt Nixon wrote:
Hi Nigel:
I know that is technically and intuitively correct but I never saw a
lick of difference in ANY digi mode I have run
between the old SB and the new 24bit/192Khz cards I have. I have
tried several different audio interfaces ( I do
commercial digital recording of everything from full symphony to
small groups). Only when I use the card for the SDR set
up do I see any actual operation difference.
In PSK, any station I could see as a trace would decode.
Not disagreeing at all with the argument for low noise cards but my
practical experience with the SB cards has been very
good.
I suspect that, especially with the Phase modulated modes like PSK,
there are some issues with phase coherence and phase
linearity thru the system that could affect decoding. Maybe I got
lucky with my two old cards.
Curt
KU8L
Nigel Gunn G8IFF/W8IFF wrote:
Although you'll copy far more station if it is high quality/low
noise, at least on the Rx side.
On 17-Sep-10 13:19, Curt Nixon wrote:
I doesn't take a high capability sound card either.
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