Re: [linrad] Mixer design - comments please

[Alex Crow <acrow@xxxxxxxxxxxxxxxxxxxx]

On Tuesday 08 July 2003 5:40 am, Edson Pereira wrote:
> Hi Alex,
>
> Since the input range of some soundcards can be in the range of 10 vpp, it
> may be better to use a 10V supply for the Op-Amps. You may also consider
> using the NE5532 instead of the NE5534 to lower the component costs.
>

I already got the 5534s for a very good price, so no worries there. I might 
modify for 10V then to get that extra bit of range.

> What type of LO source are you planning in building?

The AD9854.

>
> Looking at the DDS schematics presented in the SDR-1000 article, I don't
> understand why Gerald used lowpass filters and than a comparator if the
> DDS already has a square I/Q output.
>

The 9854 has I-Q output but they are sines (or sine and cosine), or at least a 
very good approximation. It also runs off 3.3V so you need to square them up 
and bring them to the drive level of the Analog Switch (5v).

> 73,
>
> -- Edson, 7n4ncl
>

Cheers

Alex

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