[hpsdr] Preselectior switching

[Giancarlo Moda]

Hi Phil,

I know you knew Peter's design in STAR.

I have missed some of the messages and I do understand
 the necessity of covering all HF Ham and SWL bands.

Did you look at reed relays?

73

Gian
I7SWX

--- pvharman at arach.net.au wrote:

> Hi Gian,
> 
> I actually use the PIC-A-STAR filters in the front
> end of my SDR. They work 
> fine but the IP3, even with the bus switches
> replaced with relays, is a  
> little low for Mercury.  The original design for
> Alex was based on Peter's 
> design but since we have a lot of interest in a
> tunable preselector, to cover 
> the SWL bands as well, that is what we are currently
> working on. 
> 
> 73's Phil...VK6APH 
> 
> 
> Quoting Graham Haddock <grahamh at verizon.net>:
> 
> > ***** High Performance Software Defined Radio
> Discussion List *****
> > 
> > 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.
> > >
> > >
> > >
> > >
> > >
> > >  
> > >
> > 
>
_______________________________________________________________________________
> _____
> > > No need to miss a message. Get email on-the-go 
> > > with Yahoo! Mail for Mobile. Get started.
> > > http://mobile.yahoo.com/mail 
> > > _______________________________________________
> > > HPSDR Discussion List
> > > To post msg: hpsdr at hpsdr.org
> > > Subscription help:
> http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> > > HPSDR web page: http://hpsdr.org
> > > Archives:
> http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
> > >
> > >
> > >   
> > 
> > 
> > _______________________________________________
> > HPSDR Discussion List
> > To post msg: hpsdr at hpsdr.org
> > Subscription help:
> http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> > HPSDR web page: http://hpsdr.org
> > Archives:
> http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
> > 
> 
> 
> 
> 



 
____________________________________________________________________________________
No need to miss a message. Get email on-the-go 
with Yahoo! Mail for Mobile. Get started.
http://mobile.yahoo.com/mail 

 1174138450.0