[hpsdr] General question - sampling rate vs bits on ADC

[Sid Boyce]

On 18/05/11 05:58, Dr. David Kirkby wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> On 05/18/11 05:01 AM, Glenn Thomas wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> There is an issue with using a PC sound card that has not yet been
>> mentioned. That is the fact that one winds up with a really bad level of
>> system integration. All of the extra cables between the RF hardware and
>> the PC give many additional opportunities for interface failures
>> (connector corrosion, wear) and provides additional paths for RF
>> feedback.
>>
>> If you want to find out with a fairly good SDR (better than the Soft
>> rock IMHO), see if you can find a Flex SDR-1000. That's very close to
>> the best example of a full-featured SDR that uses a PC sound card
>> (albeit a very high quality card - just any card isn't good enough, for
>> reasons described by Steve Bunch). Later Flex hardware uses the same
>> Tayloe mixer as the '1000 but include an integrated ADC/DAC - much
>> better system integration than the '1000 but the overall system isn't as
>> flexible or as high performance as HPSDR.
>>
>> 73 de Glenn WB6W
>
> Thank you. A friend and I were going to build an SDR radio, but with the
> PC components integrated into the same box as the RF circuitry, which
> would address some of the issues you describe.
>
> The sound card is a reasonably good Asus one
>
> http://www.asus.com/Multimedia/Audio_Cards/Xonar_D2X/#specifications
>
> with 24 bits (only 19.6 of which are valid based on the 118 dB S/N
> spec), 192 kHz sampling rate. The 3 dB bandwidth is <10 Hz to 46 KHz. It
> is RF shielded. My only concern was the fact there are no Linux drivers.
> (My friend chose this, and looking at it, I can't see why he did not get
> one for which there are Linux drivers).
>
> There seems to be a lot of criticism of the FM performance of the Flex
> radios. It's interesting that the top end rigs from ICOM and Yaesu use
> an FM discriminator chip for the FM demodulation despite using a DSP for
> AM, CW and SSB.
>

I have long  wondered how current the information on alsa-projects.org 
pertaining to supported cards is. I have been using an E-MU 0404 USB 
card for guitar work for about 5 years though it was said to be 
unsupported and over the last 2 years used it with Softrock SDR's. More 
recently with UAC2 kernel support 192K samplerate works.

There are instances where the D2X is said to work fine under Linux.
http://techgage.com/article/using_the_asus_xonar_essence_stx_under_linux/

Question is if you have actually tried it. I've only found one reference 
dating back to 2008 where the microphone didn't work.
73 ... Sid.

-- 
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Senior Staff Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks

 1305717131.0