[hpsdr] Odissey QSD circuit diagram

[Bob McGwier]

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
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