[Elecraft] SDR-IF and I/Q questions

[Graham Kimbell G3TCT]

David
Space diversity with the K3 is an interesting idea.
A variable phase shift could be achieved by adding the raw audio from 
main rx to a 90degree phase shifted version of itself.  Adjusting the 
relative amplitude of the 90deg version will then vary the resultant phase.

Is a phase shift at audio what's needed here, or is it a delay? I'll let 
others debate this!

73
Graham

On 19:59, David Gilbert wrote:
>
> John, do any of the SDR programs you mention allow you to monitor the 
> two audio outputs AFTER the inserted phase shift?
>
> Here's why I ask, although it is essentially unrelated to a normal SDR 
> application ...
>
> I'm convinced that we should be able to use the diversity feature of a 
> K3 with both receivers to spacially discriminate against an unwanted 
> signal.  We should be able to do it in the horizontal plane by feeding 
> two vertical antennas into the K3, one into each receiver.  We might 
> be able to partially do it in the vertical plane by, for example, 
> feeding two stacked antennas on the same tower into the K3 .... one 
> into each receiver.  All we need is a variable phase shift in the 
> audio since phase is preserved in the conversion from RF to audio.  
> I've searched for normal audio processing software to accomplish this 
> (volume equalization, phase shift, inversion, sum), but so far haven't 
> found anything other than some extremely expensive professional audio 
> stuff for large auditoriums.
>
> I've always thought that something like this could be built into the 
> K3 internal software, maybe using the VFO B knob to adjust the phase.  
> The K3 phase lock in diversity mode is not determinant (the actual 
> phase is essentially random at any frequency) so the null would have 
> to be readjusted at each frequency, but I still think it would be a 
> neat capability.  At one point (more than a year ago) Elecraft sounded 
> mildly intrigued by the idea when I first suggested it, but I don't 
> think they've spent any time on it.
>
> 73,
> Dave   AB7E