[hpsdr] SDR Dynamiic Range Considerations

[Larry Gadallah]

I thought that typically, commercial/military applications where this
issue came up were dealt with by adding a bank of octave or sub-octave
switched L-C bandpass filters ahead of the QSD/mixer. I realize that
this starts to cause problems when someone wants to monitor 160M and
10M at the same time, but it is a way to reduce the amount of energy
that the ADCs have to deal with, isn't it?

Cheers,

On 2/20/07, Rob Frohne <frohro at wwc.edu> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Bob, et. al.,
>
> When you state below that the SDR-1000 does have a roofing filter, are
> you are referring to the first order RC filter from charging the
> capacitors for the sample and hold, and/or the low pass filter in the
> sound card?  It seems from Tom Rauch's tests (see the cross post on this
> reflector entitled, "I wonder how HPSDR will affect this?"), that the
> SDR-1000 needs a better roofing filter in order to be competitive to
> those receivers using crystal roofing filters.  Perhaps Tom's
> observations and Phil's below both indicate that the SDR-1000 has some
> of the same problems you suggest Mercury and Quicksilver may have
> because the roofing filter in the SDR-1000 is not as good as it could be
> and/or because of the A/D converter voltage sensing input.
>
> I think you do have a good point that the input to an A/D converter is
> not the same as what we have been used to in a classical receiver.
> While we may get wonderful 3rd or
>
> I'm looking forward to reading more of Phil's tests.

-- 
Larry Gadallah, VE6VQ/W7                          lgadallah AT gmail DOT com
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