[Elecraft] Diversity Receive as Noise Canceling?

[Edward R. Cole]

At 10:06 PM 11/29/2010, you wrote:
>Noted your comment on noise reduction by phase nulling. Have you 
>looked on info on pages by pa0sim, see www.pa0sim.nl, he has done 
>more or less what I think you are considering. Ie connecting the 
>output from 2 phase locked receivers fed with separate antennas and 
>do the amplitude/phase nulling at AF level.
>
>Some of the sound samples on his website are impressive in terms of 
>noise reduction.
>
>I would love to see an application which could do this, would be 
>nice to check out if phase nulling works at a site before trying an 
>MFJ unit or similar. I really would like to see this done in the K3 
>as all the hardware is there to do such phasenulling in software, 
>could eg use the VFO B knob for phase control and the volume knobs 
>for amplitude control. Only requirement is to feed the 2 RXs with 
>separate antennas, ie an alternative use of diversity capability.
>
>I was not able to respond on the reflector. Would be nice if you 
>could keep the group updated if you get more info on this.
>
>73 de Olaf LA3RK

Olaf,

Thanks for writing.  I somehow lost your e-mail and wanted to look at 
the pa0sim webpage.  I merely suggested the idea.  I really have no 
prospect for doing this.  I thought maybe Elecraft might be 
interested in the idea; provide firmware to do it.

A modification on doing diversity reception was what I had in 
mind.  Use a small "sniffer" antenna on the aux Rx input to sample 
noise and null it from the main receiver in sw.  I think it would be 
easiest to accomplish in digital before conversion to audio.  All the 
DSP routines are done there:  NB, NR, AGC, APF, DSP bandwidth.  Phase 
shift and amplitude adjustments would be possible in digital, so 
assigning VFO-B would be relatively simple for phase and use the 
sub-Rx volume for amplitude adjustment.

I guess it's now up to Elecraft if they want to explore this.



73, Ed - KL7UW, WD2XSH/45
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