[hpsdr] Question - audio noise and Janus

[Robert McGwier]

Richard:

The part we are using is on the Lynx L22 and other Lynx cards:

http://www.lynxstudio.com/products.html

and the Creative Emu family:

http://www.creative.com/products/welcome.asp?category=237&

These are the finest professional audio cards and the basis for this 
fine performance is the Akashi chip.


With a lesser chip in terms of its specifications  (the one on the Delta 
44)  we take the output of the QSD/ IQ Mixer in the SDR-1000 and get  
+28 dBm IP3, and 100 dB of IMD-DR at 2 kHz (and if any lab could measure 
it,  those numbers would be the same down to a few Hz).    The 
linearity, isolation,  noise floor, etc. of the Akashi will allow us to 
exeed these numbers without changing the SDR-1000 hardware in any way.  
After Gerald and I did all of our hacking on the SDR-1000 front end, 
changing the RF amplifier,  integration time constants,  gain 
management, etc.  Gerald could not easily make changes that would 
improve that hardware.  I can attest to these facts because I own the 
Lynx L22 and the dynamic range, sensitivity, etc. of the SDR-1000 are 
IMPROVED over the Delta 44.  If would be hard for me to recommend to 
people to buy a $1200 sound card to use on a $1400 radio.  I will be 
able to recommend people use the Akashi based Janus without reservation 
unless we run into a major stumbling block.  The people involved here 
will test the thing and you can bet it will get an unvarnished opinion 
about its performance.  ;-).

Bob
N4HY

P.S.
The numbers I quote are available in the ARRL review of the SDR-1000 
available from the flex site.




Lyle Johnson wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>   
>> I appreciate that the ADC has a good noise performance, but I would be 
>> interested in the overall card noise performance in a mixed signal 
>> environment.
>>     
>
> So would I!
>
> The PCB layout is out for review.  I hope that folks with knowledge and 
> experience in this area can provide feedback to improve the layout 
> before we actually make the first boards.
>
> Then, a few boards will be made for Alpha test.  We hope to confirm the 
> design, or uncover unforeseen problems, in that phase.
>
> 73,
>
> Lyle KK7P
>
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-- 
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
Laziness is the number one inspiration for ingenuity.  Guilty as charged!


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