[hpsdr] ISD for SDR

[Ahti Aintila]

Thanks Henning,

for good suggestions. That input arrangement would look a little like
the famous QSD of Leif Asbrink, SM5BSZ. Actually, I was thinking of
that and additionally the audio feedback across the sampling switches
like Leif did. However, at this phase of the exercise, I decided to
make the circuit as simple as possible.

Maybe, later when I get more time from my other projects, I will try
Leif's ideas for a modified integrator.

Thank you again for your interest,
Ahti OH2RZ


On 31/08/06, oz1gzm <oz1gzm at skourup.com> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Ahti,
>
> It looks like a really good first attempt.
>
> I was thinking that it might be a good idea to keep high frequencies
> from reaching the OPA1632.
> That could be done by placing small capacitors at Y1 to ground and at Y2
> to ground, Combined with inductors between Y1 and OPA1632 non inverting
> input and between Y2 and OPA1632 inverting input.
>
> This way you can keep signals at frequencies the OPA1632 is not made for
> away from the OPA1632.
>
> Also a resister (100 ohm) placed across of the inductors might become handy,
> keeping the Q down when the switch is open. The resistor will not add
> much to the noise at the frequencies at interest. It is shorted by the
> inductor.
>
> Keep up the good work.
>
> Regards
> Henning Skourup
>
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at hpsdr.org
> Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> HPSDR web page: http://hpsdr.org
> Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
>

 1157045415.0