Re: [Discuss-gnuradio] Richard Hosking's quadrature DDS board

[Robert Kelley]

A quadrature DDS can be used to implement an image-rejecting mixer,
specifically a downconverter.  Multiplying a real signal from the
antenna by a complex local oscillator yields a complex result which
can conveniently be applied to two soundcard inputs.

DDS's in general can create reference signals at arbitrary frequencies,
but near the sample rate the use of those signals may be problematic,
especially as the first local oscillator of a receiver.

On Wed, 2 Jan 2002, smoerk wrote:

> could you explain the relationship between this DDS board an a
> soundcard?
>
> How expensive is it, if you build it by yourself?
>
> On Tue, 01 Jan 2002 17:02:06 -0800, John Gilmore wrote:
>
> >FYI
> >
> >Date: Mon, 31 Dec 2001 18:10:39 -0800 (PST)
> >From: Robert Kelley <address@hidden>
> >Subject: Richard Hosking's quadrature DDS board
> >
> >http://members.iinet.net.au/~richardh/Direct%20Digital%20Synthesizer%20using%20the%20AD9854%20quadrature%20DDS.htm
> >
> >This is an excellent building block for software defined radio.
> >There is nothing like it that I have been able to find.  Add a
> >pair of mixers and feed the results into a sound card and it should
> >be possible to implement a generic receiver up to 70 MHz or so.
> >A pair of phase-locked loops might be useful to clean up spurious
> >signals, however.  I have heard that the M-Audio Delta 44 is the
> >best available sound card for these purposes, short of instrument
> >grade ADC's that are out of the reach of most people.
> >
> >http://www.midiman.net/products/m-audio/delta44.php
> >
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>
>