[hpsdr] ISD for SDR

[Ahti Aintila]

On 31/08/06, Philip Covington <p.covington at gmail.com> wrote:
> On 8/30/06, Ahti Aintila <oh2rz.sdr at gmail.com> wrote:
> > ***** High Performance Software Defined Radio Discussion List *****
> 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
>

Phil,

I completely agree with your opinion about the suboptimal I/Q sampling
pulses. Having these "borrowed" pulses with toroid isolating
transformers and another line receiver certainly does not improve the
situation. However, this solution in my test layout helped in removing
ground loops that otherwise added a lot of noise.

Sorry, I dont have access to any HP8640B quality of instrument. Just
rest assured that the final layout with proper pulses will be better
than my experiment.

73, Ahti OH2RZ

 1157046578.0