[hpsdr] ISD for SDR

[Philip Covington]

On 8/30/06, Ahti Aintila <oh2rz.sdr at gmail.com> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi all,
>
> After a lot of private mailing and experiments with the Active
> Integrating Quadrature Sampling Detector concept, I think it is the
> time to put my results under the public criticism. Unfortunately, my
> previous sending bounced back due to too big attachments, so you
> should see the links:
> <http://kotisivu.dnainternet.net/ahti/sdr-1000/AIQSDb.pdf>
> <http://kotisivu.dnainternet.net/ahti/sdr-1000/isdbrd.jpg>.
>
> Against the common practice and opinions I have used 50% wide I and Q
> sampling pulses instead the 25% pulses, because those wider pulses are
> readily available without any extra decoding in proper form to the
> selected two fast SPDT sampling switches.
>
> Please, understand that my circuit is not necessarily best optimized
> for the purpose, but I feel that it is a good starting point for other
> experimenters. Already now I can suggest few dB more internal gain for
> the ISD so that no post amplifier would be needed before the sound
> card (provided that the sound card has differential inputs).
>
> 73, Ahti OH2RZ

Hi Ahti,

I just realized that you were using the SDR-1000's TRX board as a
signal source for the LO - I think that this is partially the problem
with the performance you are seeing.  The DDS and comparitors on the
SDR-1000 have been identified as part of the performance problem, so
using them as your LO is going to give you suboptimal results.

Do you have access to a HP8640B that you can drive into a johnson
counter to generate the LO for the ISD tests?

73 de Phil N8VB

 1157045803.0