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Re: LF: SDR RX ideas for grabber...

from [Andy Talbot] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: SDR RX ideas for grabber...
From: Andy Talbot <[email protected]>
Date: Sun, 21 Feb 2010 09:44:58 +0000
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Jean - Pierre...
 
Is the circuit diagram correct ?   Your two final op-amps used as differential amplifiers both have their inputs taken from teh same ndes, yet are labelled to deliver I and Q.   The first pair of op-amp do correctly take I and Q channels from the FST3253 mixer, but then their outputs are summed (differenced !)  together.   As far as I can see,   I and Q outputs are the same signal.  Also, there is very littel audio gain in the circuit, so the receiver as shown requires plenty of RF input to deliver enough audio for teh typical soundcard
 
An ERA-5 is a rather exotic device to use in the preamp - it has considerable gain right up to 8Ghz and could be difficult to kep stable.   Better to use a MAR-3 at LF.
 
On 21 February 2010 08:33, "Jean-Pierre Méré (F1AFJ)" <[email protected]> wrote:
Hi Scott ,

Please , loock at :     http://jpmere.online.fr/Grabber/Setup/Setup.htm

It is my grabber on 2200m !

73 qro Jean-Pierre f1afj


Scott Tilley a écrit :

Hi All

I was wondering if there is a simple solution that is fairly well documented for converting a softrock type receiver over to 2200m use?

Any other suggestions on how to get a SDR on 2200m with a minimum of effort would be greatly appreciated.

Regards,
Scott






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