[hpsdr] Odissey QSD circuit diagram

[Giancarlo Moda]

Hi Bob and Phil,

thanks for your comments.

I am not sure I understood your point.

My suggestion is to replace the 2C53 with the FST3125
and then connect the switches to the OPAs like with
the 53. The 74ACT74 will deliver the four phases to
the 3125.
I do not see the differences betrween the switches on
the 2C53 and the 3125.... or I misunderstood
completely the design and your comments?

73

Gian
I7SWX


--- Bob McGwier <n4hy at idaccr.org> wrote:

> Exactly.  As Phil discovered (see his blog) and as
> pointed out to us by 
> Tayloe,  we need an active integrator to provide the
> same impedance in 
> and out of band to get a good return loss for the
> filters in front of 
> the mixer.
> 
> Bob
> 
> 
> 
> Philip Covington wrote:
> 
> >***** High Performance Software Defined Radio
> Discussion List *****
> >
> >On 9/29/06, Giancarlo Moda <i7swx at yahoo.com> wrote:
> >  
> >
> >>***** High Performance Software Defined Radio
> Discussion List *****
> >>
> >>Hi all,
> >>
> >>following my previous message I like to report the
> >>following reference where you can see my idea of a
> QSD
> >>using FST3125. The output should be adapted to the
> >>ODISSEY QSD differential amplifiers.
> >>
>
>>http://it.groups.yahoo.com/group/Ciao_Radio_newsgroup_/files/
> >>then look at I7SWX QSD_06_06_comm.pdf
> >>
> >>73
> >>
> >>Gian
> >>I7SWX
> >>
> >>    
> >>
> >
> >Unfortunately, this circuit is not an improvement
> over the QSD used in
> >the SDR-1000 or the SoftRocks. There is the problem
> with using passive
> >integration - the input impedance is all over the
> place depending on
> >whether you are in band or out of band.
> >
> >Phil N8VB
> >_______________________________________________
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> >  
> >
> 
> 
> -- 
> Robert W. McGwier, Ph.D.
> Center for Communications Research
> 805 Bunn Drive
> Princeton, NJ 08540
> (609)-924-4600
> (sig required by employer)
> 
> 
> 


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