[hpsdr] Preselectior switching

[Graham Haddock]

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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