[hpsdr] Preselectior switching

[Giancarlo Moda]

Hi Graham,

the system will not accept the attachements.

certainly...here it is.
Enjoy the reading

73

Gian
I7SWX ... the one of FST3125...hi

--- Graham Haddock <grahamh at verizon.net> wrote:

> Gian:
> 
> I didn't see the attachments.
> 
> Please send them direct to me at my email address.
> 
> Thank you,
> --- Graham / KE9H
> 
> Giancarlo Moda wrote:
> > ***** High Performance Software Defined Radio
> Discussion List *****
> >
> > Hi all,
> >
> > for a receiver front end preselector I would
> suggest
> > to look at the solution used in the STAR, Software
> > transmitter and receiver, by G3XJP. The switching
> > elements are FST3125 and FST3126 as used in the
> H-Mode
> > Mixer.
> > No IMD problems and expensive relays and or PIN
> diodes
> > purchase. Fast switching, low insertion losses and
> > valid filetrs separation.
> >
> > I am attaching a copy of circuit diagram and
> article
> > extract from RadCom.
> >
> > I have added in copy VK6APH, KK7P and N8VB as they
> > will receive the attachment and then they may
> decide
> > to load it in file directory.
> >
> > 73
> >
> > Gian
> > I7SWX
> >
> >   
> >> From: hpsdr-bounces at hpsdr.org 
> >> [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of
> Henry
> >>     
> > Vredegoor
> >   
> >> Sent: vrijdag 16 maart 2007 5:48
> >> To: hpsdr at hpsdr.org
> >> Subject: Re: [hpsdr] Preselector schematic.
> >>
> >>     
> >
> >   
> >> Two observations:
> >>
> >> - There must have been a design issue for using
> >>     
> > relays on the 
> >   
> >> LOWER BANDS;
> >> maybe also the lower (zero) resistance of the
> relay
> >>     
> > contacts
> >
> >   
> >> - The are having the relays switching a (small)
> >>     
> > current on 
> >   
> >> purpose, I think
> >> to keep the contacts clean, keep the resistance
> low
> >>     
> >
> >
> > After studying the schematics a little more, I
> think
> > it prevents the 
> > (other)
> > PIN diodes from conducting, stopping the HF from
> all
> > not selected 
> > filters.
> >
> >
> >
> >
> >
> >  
> >
>
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> >
> >
> >   
> 
> 
> 



 
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