[hpsdr] ALEX - Call for Comments - II - Clarification

[Philip Covington]

On 3/6/07, pvharman at arach.net.au <pvharman at arach.net.au> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Murry,
>
> The filters in Alex will not be any use with high level inband signals.  There
> appears to be some theory regarding the performance of ADCs in the presence of
> multiple strong signals but very little practical evidence that there is an
> issue. My own testing of the prototype seems to indicate that the theory is not
> supported and the strong signal performance is excellent. Once we have a few
> prototype Mercury boards built we can submit them to kW alley and see how they
> perform.
>
> 73's Phil...VK6APH

I have the same experience as Phil with the QS1R prototype.  With in
band signals I could overload my SDR-1000 long before the QS1R and
they both seem to have similar weak signal sensitivity.  I keep seeing
these claims of the "superior performance" of QSD based designs but
then you continually hear about little bug-a-boos like their response
at 1/3, 1/5, and 1/7 the LO frequency as well as increasing NF with
frequency.  I much prefer the Mercury/QS1R design over QSD based
designs now.  The only filters I have been using on the QS1R is the 30
MHz LPF and the 1.5 MHz HPF.  Most of the time I only have the LPF
active and leave the BPF off since I haven't had any issues with
strong broadcast stations.

Phil N8VB

 1173238494.0