[hpsdr] QSD gain and noise.

[Philip Covington]

On 9/24/07, Johan Maas <johan.maas at hetnet.nl> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
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> Hello All,
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> Together with Ramkrishnan(VU3RDD) iam working on design an ISD based
> receiver by using 180 degree switches.
>
> The idea is to make use of an NCO implemented in the ozy FPGA and controlled
> via powersdr (realized).
>
> In the attachment you will find a scheme which will be used for further
> experiments (different configuration options can be set by jumpers). It
> contains an balanced and unbalanced exit.
>
> But after reading some previuos mails i think we should an additional buffer
> for low impedance output!
>
> Goodluck,
>
> 73 Johan PA3GSB

Hello,

You might want to consider replacing the fixed bias on the switches
with an adjustable source.  Look at the TI BUF01900/1  - I2C
programmable voltage source.

Also for the diff amp take a look at the TI THS4520.

I am a bit confused about the NCO in OZY.  Where is the DAC?

73 Phil N8VB

 1190639919.0