[hpsdr] ISD for SDR

[oz1gzm]

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 


 1157042932.0