Re: KX3 and Quadarature down-sampling

Posted by Alan Bloom on Jul 26, 2011; 7:00pm
URL: http://elecraft.85.s1.nabble.com/KX3-and-Quadarature-down-sampling-tp6622483p6623330.html

Hi Johnny,

I'm not familiar with the IC7800, but in general an image-reject mixer
uses the same basic principle.  It's the same as the "phasing" method of
SSB generation used 50 years ago, except that they didn't use the word
"quadrature" or "I/Q" in those days.

Alan N1AL


On Tue, 2011-07-26 at 23:31 +0800, Johnny Siu wrote:

> Hello Alan,
>  
> I have limited knowledge of radio.
>  
> Is that the operation theory of quadarature down-sampling something
> similar to the image rejection mixer in the IC7800?
>  
> Excuse me if I ask a stupid question.
>
> TNX & 73,
>
>
> Johnny VR2XMC
>
> 從︰ Alan Bloom <[hidden email]>
> 收件人︰ Gary D Krause <[hidden email]>
> 副本(CC)︰ Elecraft <[hidden email]>
> 傳送日期︰ 2011年07月26日 (週二) 11:08 PM
> 主題︰ Re: [Elecraft] KX3 and Quadarature down-sampling
>
> On Tue, 2011-07-26 at 08:44 -0600, Gary D Krause wrote:
> > I've been wondering what Quadarature down-sampling is?  This is the first that
> > I have heard of it.
>
> It's like a two-channel direct-conversion receiver.  The two channels
> are on the same frequency but use local oscillators that are 90 degrees
> out of phase.  With suitable processing, the in-phase (I) and quadrature
> (Q) mixer outputs give both the amplitude and phase of the signal.
> Among other things, that makes it possible to suppress the unwanted
> sideband of an SSB signal without a crystal filter.
>
> Alan N1AL
>
>
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