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Re: [Discuss-gnuradio] New to the group

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] New to the group
Date: Mon, 7 Apr 2003 14:25:43 -0700
User-agent: Mutt/1.4i

On Mon, Apr 07, 2003 at 04:10:26PM -0500, Paul Zawada wrote:
> Hi all
> I am starting to work in the SDR area and planning to start out by
> building myself a GNU Radio platform to play with...  Hopefully in 
> the long term I will be able to contribute to the project and add to 
> the momentum.  


> I've got a pretty good grasp on how to put something together..   I'm
> planning on using the Microtune tuner and I have a few novice questions.
> First of all, how do I get one of these units?  Do I contact Microtune
> directly or do they sell small quantities through a distributor network?
> Is there someone at Microtune that knows what the GNU Radio project is and
> may streamline the process?  

I suggest contacting Microtune.  I got a few direct from them.

> Secondly, I've seen some of the discussion regarding the Microtune eval
> board...  Has anyone built their own adaptor board?  I'm not adverse to 
> trying to roll my own on a piece of perf- or copper-clad board if the 
> consensus is that the Microtune board is a waste of $500.  

The microtune board is a pain.  It requires 4 external power supplies
and provides no way to control the AGC from the PC.  It was a useful
place for us to start, but take a look at this schematic
http://comsec.com/4937-eval-board-schematic.pdf for a much easier to
use board.  Note that that design should actually be modified such
that there are emitter followers between the output of the I2C DAC's
and the RF and IF-AGC inputs of the tuner module.  The fix for each
DAC output goes like this:

  DAC output to base of 2N3904
  collector of 2N3904 to +5
  emitter of 2N3904 to AGC input
  emitter of 2N3904 to 1K resistor
  other end of 1K resistor to ground    

> Any other tips for putting one of these boxes together?

Have fun!


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