[Elecraft] SDR-IF and I/Q questions

[David Gilbert]

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



On 11/11/2011 6:54 AM, John Ragle wrote:
> Several of the SDR programs also have an "image
> killer" available. I am guessing when I say that this "image killer"
> works by adjusting the phase (time delay)...the ones I have used are
> offset-specific WRT the particular image that is removed.
>